This article contains everything you need to know about latches.
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Latches are mechanical devices crafted to momentarily secure moving components together. By engaging firmly, they maintain the position of elements and can be activated to release and separate these parts. Popularly installed on doors and in enclosures, latches also play a critical role in seat belts, clamps, straps, and retractable systems. A range of designs provides various actuation methods, holding styles, and installation options.
Door latches are a general type of latch used for keeping doors and gates closed. They can be in the form of a sliding bolt that prevents the door from swinging open or a hook for maintaining a closed position for both sliding and swinging motions.
An example of a common door latch is a doorknob. Typically used for architectural purposes, it includes a latching mechanism, a locking mechanism, and two knobs on the interior and exterior sides of the door. The latch operates as a spring and bolt mechanism, activated by turning the knob on either side. Designed as a quarter-turn mechanism, it becomes fully engaged with a 90° rotation.
Other designs use levers instead of knobs for both aesthetics and convenience. Levers enhance the appearance of doors, blending well with various architectural styles. They also offer a better grip compared to knobs. For emergency exits, latches known as panic bars are employed. Panic bars (also referred to as crash or push bars) are activated by pushing a large bar fitted to the door handle. These latches are designed to open quickly and effortlessly, helping to prevent individuals from becoming trapped in panic situations during emergencies.
Modern doorknobs are equipped with locking mechanisms to prevent one side from releasing the latch. Many contemporary doorknobs feature advanced electrical and electronic components, offering sophisticated lock systems and electrically actuated latch releases.
Door latches can be categorized into deadbolts, deadlatches, and deadlocks, each differing in how the latch is locked and unlocked. The mechanisms, construction, and characteristics of these types are explained below.
The unique feature of the deadlatch is the smaller deadlatch bolt. The strike plate of a deadlatch is sized only to accommodate the main bolt and not the deadlatch bolt. Thus, when the door is closed, the deadlatch bolt is retracted. A retracted deadlatch bolt has a mechanism that prevents the main bolt from being pushed or retracted.
Other types of door latches include simple sliding bolts and hooks. These are commonly used on doors that experience less frequent use. Sliding bolts and hooks can be made more robust than doorknobs, as their bolts and latching mechanisms can be thicker and sturdier. Typically, these types of door latches are accessible from only one side of the door.
A simple latch consists of a base, a bolt, and a box or hole. The base, which holds the bolt, is usually installed on the door, while the box is installed on the door frame. When the bolt is slid or moved into the box, it activates the latch, securing one end of the bolt to the door and the other end to the frame.
This fundamental design has been modified to create various types of latches. Some of the most distinct types are discussed below.
Bolt latches, also known as latch bolts, are straightforward latching mechanisms that include a bolt, a handle, a backplate, a set of barrels, and a box called a striker. The barrels hold the bolt in place and secure the latch. They form a non-continuous loop that allows the handle to pass through. A bolt latch can be locked or unlocked by sliding the bolt into the socket.
The most common type of latch bolt is the barrel bolt, which is widely used for closing gates, doors, and windows.
A spring latch is similar to a bolt latch but is equipped with a spring for automatic bolt extension. Some designs use the spring to keep the bolt retracted.
Spring latches can be constructed in various ways. A typical spring latch consists of an L-shaped bolt, known as a plunger, which features a small hole for inserting a clip or pin. The backplate is designed with two lips, each with a hole, to secure the plunger. A spring is positioned between the lip and pin to maintain the plunger in its extended position.
The design of a spring latch is also utilized in deadlatches and slam latches. Deadlatches and slam latches feature distinct characteristics that set them apart from standard spring latches.
Slam latches, also known as push-to-close latches, are designed for doors that need to latch automatically when closed. Instead of using bolts, slam latches employ cams to engage with the striker or door frame. They typically have a rounded or chamfered edge to facilitate retraction upon impact with the striker. A spring-loaded mechanism keeps the cam in the raised position. When activated, the cam either turns or slides into place.
Slam latches are constructed to be more durable than standard spring latches, enabling them to endure numerous opening and closing cycles without significant wear. They are commonly used in high-traffic doors within commercial and industrial environments. Additionally, emergency exits often incorporate slam latches for quick and easy release by pushing the handle.
Additional types of push-to-close or slam latches include:
Swinging latches, also known as swinging door latches, operate similarly to slam latches. These push-to-close latches automatically engage when the door is closed. They feature a spring-loaded mechanism that keeps the bolt extended, with a rounded edge on the bolt to facilitate smooth retraction upon impact with the striker.
Cam latches are frequently used in furniture such as drawers and cabinets. They operate by turning a knob or key, which rotates an arm on the opposite side of the door. Like other quarter-turn devices, cam latches rely on a simple mechanism without needing a strike plate, box, or hole on the frame. Instead, they lock the door or enclosure by blocking only one side, making them unsuitable for doors that swing or extend beyond the frame.
Other variations of cam latches are:
Aside from hinges, handles, and guide rails, furniture such as cabinets and drawers always has a latch installed. Cabinet latches can be of various forms. The most popular are bolt, spring, cam, and slam latches.
Cabinet latches are typically crafted from materials such as stainless steel, brass, copper, and anodized aluminum. These materials enhance both the aesthetic appeal and durability of the latches, ensuring they are resistant to corrosion.
Cabinet latches are produced through various metalworking processes, including casting, cutting, and forging. As decorative items, their dies and molds are often designed with intricate patterns and shapes that go beyond the complexity of standard latches.
As the name suggests, gate latches are used for securing gates and large doors. They are made much stronger and thicker than cabinet latches. One thing in common with cabinet latches is that they can also be made with architectural design features.
Common types of gate latches include barrel bolts, bars, and heavy-duty industrial latches. In some cases, slam and spring latches are also utilized. These latches are constructed from thicker gauge sheets or plate metal and are shaped using larger compression forces.
Gate latches are typically made from galvanized steel or stainless steel, especially grade 304, to ensure high strength and corrosion resistance. These materials meet the demands of various applications across industrial, commercial, and residential settings.
This latch type resembles a cam latch in its simplicity. It operates by turning the knob 90°, which activates the latch. The mechanism involves an arm or cam that rotates when the knob is turned.
Some turn latches come with a keyed knob for enhanced security. Additionally, certain models require additional actions, like pushing or pulling, before turning the knob to release the latch. These double-action features provide an extra layer of security to prevent accidental release of the latch.
A compression latch is an enhanced version of a cam latch, designed to create a compression force between the door and the frame when closed. This compression is achieved by either pushing the door and engaging the latch or by turning the latch using a screw action. Unlike standard cam latches, compression latches feature arms that can flex slightly when pressing against the enclosure frame. These arms are thicker than those on ordinary cam latches.
Compression latches are commonly used in electronic and control equipment enclosures. They include gaskets or rubber trim along the door or frame, which are compressed by the latch to form a tight seal, protecting against dust and moisture ingress. They also help prevent unauthorized access and reduce vibrations that could cause noise and wear on door hinges.
Other types of compression latches include:
A magnetic door catch consists of a catch body fitted with a permanent magnet and a ferromagnetic strike plate. They are used to provide automatic and convenient latching of furniture doors. Other designs employ two magnets, each fitted on the door and frame. These types are used for light-duty and low-traffic doors.
The magnetic catch consists of a hollow body, typically made from non-ferromagnetic metal or plastic. Inside this body is a bar magnet, flanked by steel plates on the top and bottom sides. These steel plates help concentrate the magnetic flux and make contact with the striker plate.
Installed on the door jamb or frame, the magnetic catch works in conjunction with a strike plate mounted on the door edge. The catch can be either surface-mounted or concealed. For proper operation, the magnet and metal strike plate must make physical contact when the door is closed, ensuring a strong magnetic attraction is maintained.
A draw latch, also known as a toggle latch, features a component that remains under constant tension. This design is ideal for applications that require a strong closing force to create secure seals, preventing leaks, dust, and water ingress. Draw latches are also engineered to prevent accidental release. Common applications include electronic enclosures and equipment control panels.
A typical design of a draw latch includes two hooks: one referred to as the receiver, striker, or catch, usually made from a formed metal plate or sheet metal; and the other as the blade or claw, also made from sheet metal shaped into a hook. Some designs feature a wire or rod bent into a loop.
Latching occurs when the hooks (or the hook and loop) engage each other under tension. One hook is connected to a lever via a pin, and tension is adjusted by pushing or pulling the lever.
Subtypes of draw latches are:
Over center latches are a type of draw latch known for their minimal actuation force while delivering strong closing forces. The lever is engineered to create a mechanical advantage, allowing for significant tension with minimal effort needed to release the latch.
The term "over center latch" comes from its distinctive over center lock point. Once the lever is pushed beyond this point, the latch engages, and the closing force is maintained by the hooks.
Cane bolt latches feature a straightforward design with an L-shaped spring-loaded bolt connected to a bracket by two knuckles. To engage the latch, the bolt is turned and pushed forward into the keeper; reversing this action disengages the latch. Constructed from steel and treated to resist corrosion, cane bolt latches are available in both left and right orientations. They come with pre-drilled holes for attachment to wood or other surfaces, and some versions are designed without holes for welding directly to a door.
A pawl latch features a rotating cam that can be turned to engage or disengage the latch. A quarter-turn of the pawl locks the latch with a keeper or door frame, while a reverse quarter-turn releases it. The pawl maintains the latch in either the latched or unlatched position.
Pawl latches are commonly found on metal surfaces in various applications, including electronic enclosures, HVAC systems, buses, trailers, RVs, and boats.
Multi-point latches feature a handle connected to two long bars that extend when the handle is turned. This action engages the bars with the keepers, while reversing the handle disengages them. Also known as three-point latches, they are commonly used in doors and metal cabinets, especially for securing tall cabinets with long doors.
The handle of multi-point latches includes a rotating mechanism that turns to position the tips of the bars into the upper and lower keepers.
This action extends them sufficiently to securely engage with the frame or edge of a cabinet.
The movement of the handle locks all points of the door in a single smooth motion.
The term "quarter-turn latch" broadly refers to various latches that operate by a quarter-turn of a cam. Due to their diverse designs, these latches use a range of tools, keys, and methods for closing or opening them.
Quarter-turn latches are highly secure, designed to resist tampering and unauthorized access to enclosures. They are made from materials such as zinc, steel, stainless steel, and plastic, and are often coated with chrome or baked-on black powder. Available in various sizes and cam styles, quarter-turn latches also offer accessories like different key types, padlock cups, finger pulls, and dust covers.
A trigger latch is a distinctive type of latch that mounts flush to a door or enclosure. These compression-type latches feature a locking mechanism located below the trigger. When unlocked, the trigger is pushed, causing the pawl to drop and release the door.
Once pushed, the lever of the trigger moves upward, serving as a handle to open the door. Trigger latches can be made with or without locks and may feature raised trigger buttons for easier operation.
Twist latches, also known as butterfly latches, consist of a rotating cam attached to a straight piece called a slide, which has a curved end rotated by the cam. The latch's keeper is a flat metal piece similar to the slide, with a curved side that facilitates the connection between the slide and bracket. When engaged, the slide moves over the bracket on the cabinet, cupboard, case, or door and is secured tightly by the cam's rotation.
Twist latches come in various styles and mounting methods. They are commonly used on closures, cases, containers, shipping containers, and instrument cases. Twist latches can feature slides of different lengths and may include springs.
A rotary latch consists of a latching mechanism, an actuator, and a cable. Typically, a bolt on the opposite part engages with the latching mechanism. When activated, the cams or rotors of the rotary latch turn or rotate. It features a spring-loaded mechanism that provides a push-to-close function, similar to a slam latch.
A distinctive aspect of the rotary latch is its remote actuation capability. The actuator is connected to the latching mechanism via a cable, allowing the actuator to be positioned at a distance from the latch. Pulling the actuator causes the rotors to rotate and release the latch. Since the actuator pulls in only one direction, a spring-loaded mechanism is necessary to return the rotor to its original position.
Rotary latches can feature either single or double rotors. A single rotor rotary latch performs the fundamental function of keeping a door or panel closed. In contrast, double rotor rotary latches incorporate two mirrored single rotors placed adjacent to each other. The primary advantages of a double rotor latch include increased rigidity, due to the two rotors holding the bolt, and improved tolerance to misalignment. Additionally, double rotor latches offer wider catch openings compared to single rotor models.
Another classification of rotary latches is based on the number of latching stages. They can be either single-stage or two-stage. A single-stage rotary latch offers only the basic latching function. In contrast, a two-stage rotary latch provides two latching positions: a secondary, partially closed (false close) position, and a primary, fully closed latch. A two-stage latch must always be fully closed, but if the primary stage fails, the secondary stage helps prevent the door from suddenly opening. This type of rotary latch is commonly used in cars and other vehicles.
A hasp is a simple latch consisting of a strap and a staple. The strap is a metal plate with a slot punched on one end that fits over the staple. The other end of the strap has a hinge that attaches it to the door or door frame, allowing it to swing. The staple, the other part of the hasp, is a loop made from a bent metal rod or formed plate.
A pin is inserted through the staple's loop to secure the strap, although padlocks are commonly used instead of pins for enhanced security. Additionally, some types of hasps, known as hasp locks, incorporate built-in locks in place of the staple. Latching is achieved by rotating the lock, which secures the strap in place.
One of the earliest types of latches is the hook and eye latch. Typically made from bent wires and rods, they can also be crafted from cast metals. Casting allows them to be shaped into intricate designs, often serving decorative purposes. The hook functions as the arm of the latch, which is attached to the door, while the eye acts as the catch that receives the hook when the latch is closed.
A bar latch is another primitive form of latch, typically made from wooden or metal beams that are larger and sturdier than bolts. Due to their robustness, they are used to secure gates and large doors, designed to withstand significant bending forces and prevent the door from being forced open. The bar is held in place by strong cleats or hooks. To secure the door, the bar is either slid into a hole or lifted and manually positioned onto the cleats.
Cam locks are a type of cam latch that incorporates a key mechanism instead of a standard knob. Their primary advantage is the enhanced security provided by the lock. The base of a cam lock consists of a cylinder that fits into a hole in the door or cabinet. External threads are cut into the lateral side of the base, allowing a nut to be threaded onto these threads to securely hold the cam lock in place.
A cam lock can only be operated with the correct key, which turns the cam. Cam locks come in various forms, including different types of locks and keys. The lock assemblies are generally classified into two categories: mechanical and electronic.
Another type of lock used in cam locks is a tubular lock. Instead of being positioned radially towards the plug's axis, the tubular lock's pins are arranged circularly. These pins also have varying lengths that match the profile of the key. A tubular lock key is cylindrical and has half-cylinder notches to align the pins.
Other cam locks feature a lock that a common or universal key can release. These types of cam locks are usually seen in utility cabinets and control boxes in which more than one person is permitted to access. Also, using these types allows multiple cabinets to be accessed with just one key. These keys have standard shapes and profiles. Examples of key profiles are square, triangle, and double-bit keys.
Electronic cam locks provide several advantages over mechanical types. They offer greater convenience, as entering a code or using a fingerprint scan is often easier than handling a physical key. Additionally, electronic cam locks are programmable, allowing for key changes without replacing the entire lock. Other features of electronic cam locks may include remote control capabilities, event history tracking, and blacklist functions.
Latches come with various design features that make them suitable for specific applications. They can be crafted from different materials, finishes, and thicknesses, and may include additional features tailored to their use. Below is a summary of some general features and specifications of latches.
A door latch is a mechanical fastener that connects two surfaces or objects and provides a secure, safe, and strong connection. The latch portion of the mechanism is mounted on a flat surface such that when it meets a...
A gate latch is a locking mechanism that is used to secure gates on fences or stakes on truck beds using a metal bar and lever that is raised to open the latch and lowered to close it. Although they do not have...
A magnetic door latch is a type of latch that consists of a striking pad and a magnet and is used to keep doors and gates closed. Magnetic door latches are also known as magnetic door stops, magnetic door catches, and door magnets...
A rotary latch is a locking mechanism that secures openings such as doors, enclosures, cabinets, and panels so that they are locked and unable to accidentally open. They are referred to as slam latches since...
Rubber latches are latches made of rubber or are composed of rubber components. They are used in the automotive, aerospace, and medical equipment industries due to their flexibility, durability, and non-abrasive properties...
A spring latch is a mechanical device that is utilized in the joining of two separate components in order to prevent movement or opening. A spring latch is locked with a spring compression so that it will not be released...
A hinge is a movable joint or mechanism that joins two items together. The hinge is one of the most popular categories of mechanical bearings. Butt hinges are a particular kind of hinge that have rectangular pieces that...
A concealed hinge, also known as a hidden or European hinge, is a type of hinge that has parts invisible to the onlooker when the door is closed. They are commonly used in cabinet doors to add an aesthetically pleasing and...
A continuous hinge is an extended single unit hinge that spans the full length of a door, cabinet, lid, or enclosure entrance. They are made of lightweight metals and can be cut to fit the size of any opening...
An eyelet is a metal, rubber, or plastic ring with flanges are used to strengthen or reinforce holes punched in thin fabrics. It is a smaller counterpart of a grommet that is bigger in size and used for more heavy duty materials...
A hinge is a machine element that connects two bodies allowing angular movement about a fixed axis of rotation, all the while preventing translations and rotations on the remaining two axes. A hinge can be...
A fastener is a non-permanent or permanent mechanical tool that rigidly connects or affixes two surfaces or objects together. Non-permanent fasteners can easily be removed without damaging the joined materials...
A friction hinge works by creating a specific tolerance in between the mechanical components. It works based on the principle of torque that can be achieved by applying a desired amount of force. Some other additions to these hinges such as...
A lock is a mechanism designed to connect an opening to its frame using a latch, solid cylinder, bolt, or some other form of a solid metal plunger that extends into the strike. They are metal devices that prevent entry or access for privacy, security, or...
A metal washer is a small flat piece of metal that has a hole in the center and is used as a spacer, a method for absorbing shock, or distributing the load of a fastener. The hole in the middle of a metal washer allows for a bolt or screw to pass through...
A self-drilling screw is a type of tool that has the same design features as a drill bit or cutting tool. As the name implies, self-drilling screws do not require a pilot hole in order to perform as a fastener...
A spring hinge is a self-closing hinge that automatically closes two connected workpieces using the action of a spring that is loaded into the hinge's barrel. They can be found in a wide variety of products such as...
Stainless steel hinges connect two components while allowing them to move in relation to one another. They can have various leafs shaped like rectangles and other forms depending on the type of stainless steel hinge. Stainless steel hinge leafs are...