Mortise lock

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Mortise lock (vertical design)
In the horizontal design, the nut and keyhole are arranged side by side.
Interior view with the lock cover removed

The mortise lock (also mortise lock ) is a door lock with latch and bolt according to DIN 18 251 for installation in butt, rebate or tubular frame doors. A tubular frame door is also referred to as a tubular frame lock, which is a particularly narrow variant of the box lock.

Mortise one can warded - Zuhaltungs- or cylinders have factory closing or via Badriegel blocked. Compared to the historical box locks that were attached to the inside of the door, mortise locks cannot be seen when the door is closed and therefore cannot be manipulated from the inside. On the other hand, the door leaf is weakened by the recess necessary for the mortise lock.


  • The latch is the angled bolt that snaps into the corresponding opening of the strike plate under the pressure of the latch spring when the door falls into the lock .
  • The axial dimension describes the distance between the center of the latch and the nearest edge of the door leaf or the outer edge of the strike plate.
  • The web dimension describes the distance between the long side of the latch and the nearest edge of the door leaf or the outer edge of the strike plate.
  • The lock bolt is usually located below the latch in the faceplate (the sheet metal of a built-in mortise lock that is visible in the door rebate) and is pushed into another opening in the strike plate with the aid of the key after the door has been closed to lock the door.
  • The change is a push rod inside the lock to be able to open the latch of house or apartment doors with a fixed knob by turning the key.
  • The handle follower is the central, round insert in the lock through which the square of the door handle is guided. After actuating the door handle, the follower spring (also known as a counter spring) ensures that the follower , square and door handle move back into their original position.
  • Lock bottom and lock cover are the lower and the upper lock plate, behind the face plate to the box form (body) of the lock.
  • The tumbler consists of movable metal sheets inside the lock, which are pressed into recesses in the bolt by the tumbler spring in order to secure it in its position until it is unlocked by a suitable key and moved forwards or backwards.

Alternatively, there are the recesses in the Zuhaltungsblech itself, which is raised by the key rotation to a fixed on the bolt lock pin release (turn pin), and thus to enable the movement of the bolt. Chubbschlösser contain several of these tumbler plates, which are lifted to the correct height by the respective shoulder of the stepped (serrated) beard of the associated tumbler key in order to release the bolt.

As an example, the designation of a mortise lock as a tumbler lock (BB), backset 55 mm, right-hand lock in resistance class 1: "Lock DIN 18 251 BB 55 Rl".

Selection of the opening direction

The latch protrudes from the faceplate (reversible here) and the latch protrudes from the bottom

When choosing a mortise lock, pay attention to the opening direction of the door. The manufacturers usually identify the opening direction as "R" (right) or "L" (left) in the article description. If the latch can be turned (on the removed lock), the lock can be used for doors that open on the left as well as on the right (see illustration).

Turning the latch is now usually possible without opening the lock housing, but usually only when it has been removed. Often a small slide, which protrudes in one of two recesses on both sides of the housing, has to be pushed to one side and then back again. To turn the latch, it must either be pushed deep into the housing or pulled out; the hammer-shaped double-sided driver and the wedge-shaped latch itself can only be rotated 180 degrees around the displacement axis in one of these positions.

Suitable for a door that closes on the left, the pointed edge of the latch is on the left when looking at the faceplate.


Backset: Distance from the center of the keyhole and square pin to the outer edge

The backset describes the distance from the center point of the keyhole and square pin to the outer edge of the faceplate. It is usually given in millimeters. Backsets are usually in the range of 20 to 100 mm. 55 mm is normal for wooden room doors, 65 mm for solid house doors, 24/30 mm for (glazed) tubular frame doors and 40–45 mm for fire doors made of metal.

Occasionally even that will rear backset specified: backset + rear backset = insertion depth. The insertion depth (box width) is decisive when installing in an existing door leaf.

Distance measure

Also called distance standard or hole center distance .

To select the right door fitting (handle set), the distance between the center point of the axis of rotation (square) of the door handle and the pivot point of the lock cylinder must be taken into account. In Germany, this is usually 72 mm for room doors with tumbler keys and 72 or 92 mm for doors with profile cylinders (PZ). Distance dimensions between 47 and 110 mm are also available as custom-made products.

country application Distance in mm
Germany Room door (tumbler or PZ) 72
Germany front door 92
Germany Escape door / panic lock 92 or 72
Germany Toilet door 78
Switzerland 78
Austria Mustard (room door) 90
Austria Profile cylinder (front door) 88 (more rarely also 85 and 90)
France front door 70
France room door 70 or 72
England front door 48
England room door 57
Netherlands room door 56
Netherlands front door 55, 72 or 85
Belgium room door 72 or 90
Belgium front door 72, 85 or 110
Czech Republic room door 72, 90
Czech Republic front door 72, 90, 92
Hungary 90

Handle follower and handle (square)

The pusher mandrel connects the door handle with the follower , which the movement of the door handle to the latch transfers. It is also known as a square , square pin , mandrel pin or simply pin . The handle follower has a square hole into which the handle pin is pushed.

The square dimensions of the handle follower have been reduced to three common dimensions in Germany in recent decades: 8 × 8 mm for room doors, 10 × 10 mm for house and robust apartment entrance doors and 9 × 9 mm for fire doors and panic locks . Internationally, the size of 8 × 8 mm is the most common. In contrast, toilet bars can have quite different dimensions, down to 5 × 5 mm (England). In addition to the dimensions given in the table, the dimensions 7.6 × 7.6 mm are rarely used.

country Square dimensions in mm
Germany (general) 8th
Germany (panic locks & fire doors) 9
Germany (some front doors) 10
France 7th
France 8th
Austria 8.5

With escape and panic doors , the square is often in two parts. One part then has a longitudinal bore through which the other part can be connected to a screw with a tensile strength, but rotatably against one another. The divided square bar enables the handle on the inside of the door to trigger a different function than the handle on the outside. In the case of a panic door, for example, the door should also open when the handle on the inside is pressed, even if the door has been locked with a key.


The faceplate

The faceplate (also: the faceplate ) of a lock is the sheet metal part that is still visible after installation and is embedded in the door edge. It usually has two holes for the fastening screws of the lock, two recesses for the latch and the bolt and, if necessary, a hole below the bolt for the fastening screw of the profile cylinder. The width, length and thickness of the faceplate, the design of its ends (round or rectangular) and the distance between latch and bolt are not uniform. Typical are e.g. B.

  • Width: 18, 20 or 24 mm
  • Thickness: 3mm
  • Length: 235 mm (at 72 mm distance / room or corridor door) or 280 mm (at 92 mm distance / front door)
  • Distance from the lower edge of the latch to the upper edge of the bolt (frame dimension): 50 mm


  • Lock DIN 18 251 - 1: Locks - Mortise locks - Part 1: Mortise locks for rebated doors
  • Lock DIN 18 251 - 2: Locks - Mortise locks - Part 2: Mortise locks for tubular frame doors
  • Lock DIN 18 251-3: Locks - Mortise locks - Part 3: Mortise locks as multi-point locking
  • Lock DIN EN 12209: Locks and building hardware - Locks - Mechanically operated locks and striking plates

Individual evidence

  1. Rudifeira / Feichtinger / Gromer / Hauer / Kaiser / Piegler / Raich: Metalltechnik. Basic and specialist knowledge . In: Verlag Jugend & Volk GmbH, Vienna. (Ed.): School book . No. 115545 . Jugend & Volk, Vienna 2012, ISBN 978-3-7100-2713-0 , p. 275 ff .
  2. See also the illustration at KoksaWiki.
  3. Galbusera ( Memento of March 28, 2012 in the Internet Archive ) (Italian manufacturer), PDF page 54
  4. Ordering information ( Memento of the original from March 21, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. of the company retail trade for fittings and components , Fürstenwalde / Spree, accessed in February 2016 @1@ 2Template: Webachiv / IABot /
  5. ^ Catalog from Gege or Kaba GmbH , Herzogenburg, Austria, accessed in February 2016
  6. Lexicon security technology: Stulp, Stulpe In: , accessed on August 10, 2017.
  7. DIN 18251-1: 2002-07 In: , accessed on August 10, 2017.
  8. DIN 18251-2: 2002-11 In: , accessed on August 10, 2017.
  9. DIN 18251-3: 2002-11 In: , accessed on August 10, 2017.
  10. DIN EN 12209: 2004-03 In: , accessed on August 10, 2017.

Web links