Mortise Lock

Main parts of a mortise lock

A mortise lock fits into a pocket cut into the edge of a door. The Lock Case contains the operating mechanism; the Lever Knobs and Cylinder Unit let the user operate it from the door faces. The Faceplate is the plate visible on the door edge. The Strike Plate is a different component, fixed to the frame where the bolts engage. Schlage's mechanical-lock guide explains this arrangement.

This BOM illustrates a mechanical lock with a spring latch and a manual deadbolt. It is not a teardown of a named product. Mortise locks also come in latch-only, nonkeyed and other configurations, so the presence of a cylinder or deadbolt should not be assumed from the word mortise alone. Schlage's L Series function list shows these distinctions.

Latching is not the same as locking

The beveled Latch Bolt can move inward as the door closes, then the Latch Spring pushes it into the strike. Whether an outside handle can retract it depends on the lock function. A passage set has no means of locking, while a storeroom function keeps the outside handle inoperative. An office function can allow the outside handle to be left locked or unlocked. These are different mechanisms and uses, not interchangeable names. Allegion describes the common functions.

The Deadbolt in this example is moved deliberately by the key or an inside operator. It does not project merely because the door closes. Springs can still be present in the deadbolt's operating mechanism: a spring acting on a hub is not the same as a spring automatically throwing the bolt. The exact role of the modeled Deadbolt Spring requires a product-specific parts drawing.

The cylinder supplies the keyed input

The cylinder is the keyed input to the lock mechanism, not the whole lock. This example groups a plug, housing, five key pins, five driver pins, springs and a mortise cylinder cam. The five pin stacks describe this diagram only. Actual cylinders can use other pin counts and key systems.

The cam transfers cylinder rotation to the lock mechanism. Cam shape and cylinder size must match that mechanism; a similar-looking cylinder is not necessarily interchangeable. Schlage's cylinder documentation distinguishes mortise cams from the tailpieces used in cylindrical locks.

What the BOM counts

The faceplate is a physical item. Its material and surface finish describe that item; a polished or plated surface is not another assembled component. Here the faceplate branch contains the faceplate strip and its mounting fasteners. The historical finish node remains available, but is not counted as a separate part in this assembly.

Fastener sets and grouped hardware are also modeling units. The displayed total therefore describes this BOM's entries and quantities, not a verified count of every screw, washer and manufactured piece in a real lock. Manufacturer parts lists, such as the Schlage L Series service manual, distinguish individual parts from service packs.

Identifying replacement parts

Before using the list to find a replacement, identify the manufacturer, lock series, operating function, handing and door preparation. Check the corresponding parts drawing and installation template. This generic diagram does not establish fit, a performance grade, expected lifespan or suitability for an exit door.

Cylinder service is design-specific. For example, an appropriate control key removes a Schlage small-format interchangeable core without dismantling the lock. That is not the procedure for every cylinder. Use the identified product's service instructions or a qualified locksmith; drilling a retaining part is not a general rekeying step.