What is the lock-side gap?
The lock-side gap is the clearance between a hinged door or opening casement and its frame on the side where the lock sits. In Dutch it is called the sluitnaad. The gap on the opposite side is the hinge-side gap. Together with the gaps at head and threshold, they let the door swing freely even when the timber swells with moisture.
Characteristics
- Leading edge bevel. The lock edge of a timber door is usually planed with a slight bevel so it clears the frame as it closes.
- A security weak point. A gap that can be reached from outside gives a screwdriver or crowbar something to bite on. The wider the gap, the easier it is to lever the door.
- Hidden on rebated doors. A rebated (lipped) door overlaps the frame, so the gap is not exposed from outside.
Application
- Plane the hinge side. If a door sticks and must be trimmed, take material off the hinge edge. The lock edge already carries the bevel, the lock and the strike plate.
- Allow for damp. Doors to sheds, outbuildings and other damp spaces benefit from slightly more clearance, because the timber moves more.
- Cover the gap on external doors. A steel anti-jemmy strip (security strip) fitted to door and frame covers the gap and makes levering much harder.
- Combine with good hardware. A covered gap works best with a multipoint lock and burglar-resistant hardware.
- Wait before adjusting a new build. Doors and frames move most in their first year. Adjust the hinges after a heating season if the gap is still uneven or tight.
Common mistake: planing the lock edge square, or taking too much off it. The latch then fails to engage properly in the strike plate and the gap becomes wider and easier to attack.
Related terms
- Hinge-side gap
- Rebated door
- Multipoint lock
- Anti-burglar hardware
- Burglar resistant
- SKG
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