Locksmith glossary

A system that manages who can enter, through which door and when, using keys, cards or electronic credentials. Electronic systems are not part of our services.

An extra lock, usually surface-mounted, that reinforces the main lock. It is operated with a key from outside or with a knob from inside.

A strike plate that lets you slightly shift the part that receives the latch or the bolts to adjust how they engage. It is screwed to the frame, opposite the lock.

A feature of a cylinder designed to resist the impact opening method known as bumping. The level of resistance depends on the model and should be stated in its documentation.

Protection of a cylinder or lock with hardened parts that make them harder to drill through.

A cylinder’s resistance to being pulled out of the lock. It depends on the cylinder’s design and on the escutcheon and the door protecting it.

A set of features that make it harder to lever the door leaf away from the frame. It depends on the whole door, not on a single part.

A cylinder’s resistance to having its mechanism manipulated with tools other than the key. No cylinder is invulnerable; the level is shown in the model’s documentation.

A cylinder design that keeps the lock locked if the outer part is forced until it breaks. It is not the same as anti-drill.

A trade term for doors, usually timber, reinforced with sheet metal. Their construction varies a great deal and is worth checking in each case.

The measurement of a lock from its forend to the centre of the cylinder or spindle. It is not the same as the keyhole.

A locking element that comes out of the lock when the key or the privacy bolt is operated and, unlike the latch, has no spring.

The part fixed to the frame that receives the sliding bolt of an additional bolt. If it shifts or its screws work loose, the bolt no longer goes in straight and becomes hard to slide across.

A term used in some areas and catalogues for the levers of a lock and, by extension, for locks that work with them. See levers.

The part that turns with the cylinder plug and operates the lock mechanism. Its shape and position depend on the system.

The part that recognises the correct key and transmits its turn to the lock mechanism. In everyday language it is also called the barrel.

The long screw that passes through the lock and holds the cylinder in place. You can see it on the lock forend, with the door open, at the height of the cylinder, and it is the reference point for measuring each side of the cylinder.

The part of the cylinder that sticks out beyond the outside face of the door or the escutcheon. The more it sticks out, the more exposed it is, which is why it is measured before choosing a cylinder or an escutcheon.

A flat key with round dimples on its faces instead of teeth along the edge. It is used with cylinders designed for that type of key.

A device that returns the door to its closed position in a controlled way after it has been opened. It does not lock the door: the lock does that.

The side of the door leaf that you see when the door is open. It shows the lock forend and, in many cases, the cylinder.

The fixed structure around the leaf that holds the hinges and carries the strike plate.

The direction in which a door opens, left or right, depending on the side the hinges are on. It matters for locks, latches and hardware that do not work the same way in both directions.

A lever that, when turned, operates the latch to open the door.

Any fitting on a door, such as hinges, handles, pull handles or locks. Not all door hardware locks the door.

The moving part of the door, the part that opens and closes, as opposed to the frame, which is fixed.

A service to get in when a door cannot be opened with its key. It is carried out after checking the right of access of the person requesting it.

The recess in the frame that the leaf rests against when it closes. You can see it along the frame when the door is open; if the leaf hits it or does not sit properly, the door may rub or close badly.

A device, such as a chain or a hinged arm, that lets the door open only a few centimetres. It is fitted on the inside face, between the leaf and the frame.

A viewer fitted in the leaf so you can see outside without opening the door. It is not part of the locking system.

A function of some cylinders that lets you open with a key from one side even when there is another key in the opposite side. It depends on the cylinder model.

A cylinder that takes a key on both sides of the door. It should not be confused with the double clutch, which is an additional function.

A strip of rubber or another flexible material that seals the gap between the leaf and the frame. It is usually fitted or stuck into the rebate; if it is too thick or comes loose, you may have to push the door for the latch to engage.

In pin tumbler cylinders, the part sitting above each pin that, pushed by a spring, stops the plug turning unless the correct key is inserted.

A door whose leaf has sunk relative to the frame because of hinge wear or its own weight. You can tell because it rubs at the top or bottom and the latch or locking points no longer line up with the strike plate.

A key with teeth or cuts along the edge, the most common type. Its type does not by itself indicate a level of security.

A strike plate with a mechanism that releases the latch when it receives power, for example when the door entry system button is pressed. It is also called a door release. It is neither a cylinder nor a motorised lock.

A lock whose mechanism can be operated electrically, as well as manually on many models. Each model needs its own power supply and compatibility.

A rod mechanism that locks the leaf at the top and bottom when a handle is turned. It is common on windows and double doors, and different from a separate bolt.

A cylinder with a standardised cross-section, very common on front doors. It is measured from the central fixing screw to each end, and the measurements should be checked before replacing it.

An elongated plate screwed to the leaf on which the handle is mounted, sometimes with the cylinder hole included. It can be seen on both faces of the door, at the height of the lock.

The spring that returns the handle to its position after it has been pressed down. It may be inside the backplate, the rose or the lock itself; when it wears out, the handle droops.

A door with an internal steel structure designed to offer greater resistance. Its real performance depends on the model and its documentation.

A fitting that joins the door leaf to the frame and lets it swing. A loose hinge makes the door drop and can stop it closing properly.

A hook-shaped locking point that engages in the strike plate and makes it harder to separate the leaf from the frame. It is used on some multipoint locks and sliding door locks.

On a key, the part that goes into the lock and carries the cuts or teeth. On lever keys, the flat stepped piece that moves the levers.

The part of the key you hold between your fingers. It usually carries an engraved brand or number, and it is where cracks sometimes appear from daily use.

A key made from another one. If it has been copied inaccurately it can be hard to turn even when the cylinder is fine, and on some systems copies can only be ordered with the key registration card.

The shape of the key’s cross-section, which must match the keyway of the cylinder. Keys that look alike may have different profiles and not fit the same cylinder.

A card or document supplied with some high-security cylinders, which the owner presents to order copies or compatible cylinders. Its number should not be published or sent in a photo.

A full turn of the key that moves the lock’s bolts out. A door that has just closed on the latch has not been deadlocked; with the key turned, the bolts work as well as the latch.

Several cylinders set up to be opened with the same key. It differs from a master key system in that all the keys open the same doors.

The opening through which the key goes into a lock, or the decorative piece around it.

A round control for opening the door. The term is also used for the inside control of a thumbturn cylinder.

Another name for the latch bolt, referring to its bevelled face, which slides over the strike plate as the door closes.

A bevelled, spring-loaded part that engages in the strike plate by itself when the door closes and is drawn back with the handle or knob. It is also simply called the latch.

Plates inside certain locks that only line up with the bit of the correct key, allowing the bolt to move. Locks that use them are called lever locks.

A pivoting fitting made of two parts that fit onto a pin and can be separated by lifting the leaf. It is a type of hinge.

The mechanism that keeps the door closed and is operated with a key, cylinder or handle. The cylinder and the escutcheon are separate parts from the lock.

The everyday name for a lock’s cylinder, the part the key goes into. See cylinder.

The metal body that houses and protects the internal mechanism of a lock.

The metal plate of the lock visible on the door edge, through which the latch and the bolt come out and which is used to fix the lock to the leaf.

The recess cut into the door leaf to house a mortice lock. Its dimensions must match those of the lock.

A place where the mechanism secures the leaf to the frame, by means of a bolt, a round bolt or a hook.

Within a master key system, a key that opens several cylinders that also have their own individual keys.

A way of organising a set of cylinders so that each key opens only the doors it is authorised for, while a higher-level key opens several at once. It is common in residents’ associations, businesses and hotels.

A cylinder made of parts that the manufacturer allows to be combined or adjusted, for example in length. The options depend on each manufacturer and model.

A lock housed inside the door leaf, of which only the forend on the edge and the controls can be seen.

A lock that secures the leaf to the frame at several points along the edge and sometimes at the top and bottom. More points do not by themselves guarantee more security.

A long, slim lock designed for doors whose profile leaves little room, such as many aluminium doors. It sits inside the profile and its forend can be seen on the edge.

A portable, stand-alone lock with a shackle that hooks onto another part. It is not fitted into the door like a lock.

A horizontal bar that opens the door from the inside when pushed, designed for emergency exits. Whether it is used in a given building depends on the applicable regulations.

In a pin tumbler cylinder, each of the parts the key sets at the correct height so that the plug can turn. In other mechanisms the term refers to a locking pin.

Slack or excess space between two parts that should fit closely, such as the leaf and the frame or the cylinder and its hole. You notice it when the closed door moves when pushed or when a part wobbles when touched.

The rotating part of the cylinder that the key goes into. It only turns inside the body when the key is the correct one.

A lock operated from the inside, with a button or a knob, to lock the door, as on bathroom doors. It cannot be used to get in from outside.

A fixed grip for pulling or pushing the door. Unlike the door handle, it does not operate the latch.

A complementary plate fitted on the opposite face of the door or on the frame to fix or reinforce a part, such as an escutcheon or an additional bolt. Its shape depends on the product.

A key that can be inserted into the cylinder in more than one position, for example either way up.

A lock fixed to the inside face of the door, with its case visible. It differs from the mortice lock, which sits inside the leaf.

A decorative part, usually round, that covers the hole in the leaf around a handle, a knob or a cylinder. It appears on both faces of the door and does not protect the cylinder the way an escutcheon does.

A solid locking element, usually cylindrical, that comes out of the lock forend and goes into the strike plate. Unlike the latch bolt, it has no spring and no bevel.

A security container for keeping money, documents or valuables. It is not a front door and opening it is not part of our services.

An outer part that surrounds and covers the cylinder to make it harder to attack. It must match the size of the cylinder and the thickness of the door.

A lock that secures the leaf to the frame at a single point, even though that point may have one or several round bolts.

A metal bar that slides to lock the door by going into its housing in the frame. It is the moving part of an additional bolt or a surface-mounted bolt.

A square-section bar that passes through the lock and joins the handles or knobs, transmitting their turn to the latch.

The part fixed to the frame that receives the latch, the bolt or the round bolts of the lock when the door closes.

A screw that passes right through the leaf to join an outer part to an inner one, as on many escutcheons and plates. It is hidden on the outside and can be seen from the inside face of the door.

A cylinder with a key on one side and a knob or thumbturn on the other, so you can lock or unlock from inside without a key.