pan

In carpentry and joinery, a pan is the shallow rectangular recess or mortise cut into the edge of a door frame, door leaf, or hinge stile to accommodate the leaf of a butt hinge. The hinge leaf sits fully within this recess so that the knuckle, or barrel, of the hinge protrudes just enough to allow the door to swing freely without binding against the frame.

The depth of the pan must match the thickness of the hinge leaf, typically 1.5 to 3 mm depending on hinge type and size. If the pan is too shallow, the hinge will stand proud and prevent the door from closing; if too deep, the hinge will rattle and wear prematurely. The length and width of the pan correspond exactly to the dimensions of the hinge leaf itself. Pans are usually cut with a mortise chisel or router, though on production work they may be drilled and chiseled, or cut by CNC.

A door or frame typically requires two or three pans, one for each hinge. On a standard residential 2040 mm tall door, the top hinge sits about 150 mm down from the top edge, the bottom hinge about 225 mm up from the floor, and a middle hinge (if present) equidistant between them. Both the door edge and the frame edge must be panned; the pan in the frame is often called a frame pan to distinguish it.

Errors in panning are common and costly. A pan cut off-center will cause the door to swing unevenly or slam shut. A pan positioned too far in from the edge leaves no material to hold the hinge securely. Poor chiseling around the perimeter leaves the leaf loose. On external doors, a pan cut too deep can expose bare wood susceptible to moisture ingress.

The term likely derives from the pan of a balance or scale, referring to any shallow receptacle, or from the flat bottom of a cooking pan. In older joinery texts, the recess is sometimes called a hinge pocket or simply a mortise, though mortise is now broader and less specific. The quality of panning work distinguishes handmade or bespoke joinery from factory-built components.