A mortise lock houses its latch and locking mechanism in a case inserted into the door edge. Explore the latch and deadbolt motion, then compare the case and pocket dimensions with the measured stile width and door thickness.
Mortise Case and Door Envelope Calculator
Enter measured stile width, lock-case depth, door thickness and mortise-pocket thickness. The worksheet reports remaining back and centered side ligaments plus simple occupancy percentages. It does not approve a door preparation, installation, security grade or structural capacity.
Equation Used
- Stile width and case depth are measured inward from the same door-edge datum.
- Pocket thickness is centered through the entered door thickness only for this arithmetic view.
- The animation illustrates separate latch and deadbolt actuation without modeling a particular product function.
- Material strength, reinforcement, fire rating, security grade, clearances, fasteners, trim and code compliance are excluded.
Compare case depth with stile width and pocket thickness with door thickness as separate measurements. The remaining material describes fit geometry, not structural strength or a security rating.
Case in the door edge; latch and deadbolt inside the case
A mortise cavity receives the lock case from the door edge and a faceplate closes the edge preparation. Depending on the selected function, a lever hub can retract a spring latch while a cylinder or thumbturn cam controls a separate deadbolt or locking function.
Functions, trim holes, handing and internal details vary by product. The animation is a neutral topology diagram, not a drilling template.
Compare measured envelopes before consulting the template
The calculator can expose obvious dimensional conflicts between a measured door section and a selected case envelope. Final preparation must follow the exact manufacturer's current template and instructions and account for the door and frame construction, reinforcement, fire listing, accessibility and applicable code.
Two section-view residuals
Measured-envelope example
For a 140 mm measured stile and 100 mm case depth, back ligament is 40 mm. For a 45 mm door with a centered 21 mm pocket, each side ligament is 12 mm. These values describe geometry only.
Two door sections, two different measurements
Case depth extends inward from the door edge, while pocket thickness extends across the door thickness. Keeping these perpendicular measurements separate shows the remaining material behind and beside the case. Suitability also depends on the door construction, reinforcement and the selected lock template.
Mortise-envelope questions
Does a positive back ligament approve installation?
No.
Is a centered pocket always required?
No; follow the selected product template.
Are backset and case depth the same?
No. Backset locates a spindle or cylinder center from the door edge; case depth is the overall inward case envelope.
Mortise-lock references
- Schlage Commercial, L Series Mortise Lock: official product resources, case dimensions, service manual and product-specific door templates.
- dormakaba/BEST 34HW–35HW installation instructions: separate lock-case cavity and faceplate preparation with product-specific depth.
- dormakaba/BEST 34H–37H installation instructions: mortise cavity, case installation, trim and cylinder sequence.
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