The Schlage 40-158 is the OEM L Series mortise pocket filler for the door edge, listed in the Schlage L Series Service Manual alongside the 40-160 mortise lock jig, 40-227 L Series installation templates, and 40-286 universal clamp. This places it squarely in the professional installation and conversion toolset for the Schlage L Series, mortise lock -not a lock component that wears or fails in service, but a precision installation piece used by locksmiths and door hardware contractors when the mortise pocket at the door edge needs to be correctly filled, sized, or finished for L Series lock case installation.

The "(edge)" designation identifies the application site: the latch edge of the door -the narrow face that is visible when the door is open, where the mortise front plate and latch bolt protrude. This is distinct from the door face (the broad flat surface) or the lock case body itself. The filler specifically addresses the door edge portion of the mortise pocket.

Why the Mortise Pocket Edge Needs a Filler

The mortise pocket is the rectangular cavity cut into the door edge to house the mortise lock case. The L Series lock case has precise dimensions: 4-7/16" x 6-1/16" x 1" (113 mm x 154 mm x 25 mm) with a 2-3/4" backset and a lock front measuring 1-1/4" x 8" x 7/32". For the L Series lock front to sit flush against the door edge, the mortise pocket must be cut exactly to these specifications -the right width, height, and depth.

In new installations on new doors prepared specifically for the L Series, the pocket is cut to spec from the template and the filler may be used to ensure the lock front is seated at the correct depth with no gap between the lock front and the door edge face. In conversion scenarios -where an existing door carries a different mortise lock and the existing pocket dimensions do not match the L Series profile -the 40-158 filler fills the void at the door edge between the installed L Series lock front and the surrounding door material. This prevents air infiltration through the gap, maintains the structural integrity of the door edge, eliminates the aesthetic gap visible from the corridor side, and provides a clean surface for the lock front to fasten against.

Schlage L Series Mortise Lock Parts: Installation Tool Family

The 40-158 pocket filler sits in the Schlage L Series installation tool family documented in the L Series Service Manual. The full set for professional L Series mortise lock installation includes:

40-158

Mortise pocket filler, door edge.

40-160

Mortise lock jig -the complete boring and case jig set including the case, jig, long boring shaft, 3/4" wood cutter bit, 1" wood cutter bit, 1-1/8" wood cutter bit, and instruction booklet.

40-227

L Series installation templates for all trim configurations (rose L1, rose L2, escutcheon L1, escutcheon L2, wood door L3).

40-286

Universal clamp for securing the jig to the door during boring.

Together, these four tools cover the complete L Series door preparation and installation process from initial pocket routing through final case seating. The 40-158 fills the gap between the jig-based boring step and the final lock front installation, specifically addressing the door edge interface.

Schlage L Series Mortise Lock: Door Edge Requirements

The L Series Service Manual includes specific notes for the door edge mortise pocket. Metal door applications require reinforcement behind the mortise pocket per the service manual -the 40-227 template positions this reinforcement opening and the lock pocket together. For lead-lined door applications, 1/8" (3 mm) is added to the mortise pocket width. For electrified L Series installations (MLR chassis, EL/EU functions), wire routing provisions must be planned at the door edge stage before the mortise pocket is fully prepared.

The 40-158 filler supports all of these applications by ensuring the final door edge condition is correct for the L Series lock front before the lock is fastened.