miters

Miters, or miter joints, are angled cuts at the ends of two pieces to form a corner. When joined, the two pieces create a clean, single line on the exterior. The most common case is a 90-degree corner formed by two 45-degree cuts, but any corner angle can be accommodated by adjusting the cut angles on each piece.

Inside miters form corners on the interior angle of a frame; outside miters form projecting corners. For a corner of angle A, each piece is cut at an angle of (180 - A)/2 relative to its length. In crown molding or other non-perpendicular corners, compound miters combine a miter with a bevel.

Cutting tools include a miter saw, which makes crosscuts at precise angles, and a miter box with a handsaw for fixed angles. Accurate miters require square stock, precise measurement, and tight joints; glue is typical, and mechanical fasteners provide additional strength. Clamping prevents misalignment during assembly.

Miters are widely used in picture frames, window and door casings, baseboards, and cabinetry trim. The term mitre is the British spelling; miter is the American spelling.

Limitations include wood movement with humidity, which can open gaps if joints are not properly supported. In some cases, coping joints, spline reinforcement, or mechanical fasteners are used to improve fit and long-term stability of longer molding runs.