Mitre box

Also called: miter box, mitre block

A mitre box is a trough-shaped guide that holds wood steady and directs a saw along a set angle to cut a mitre, an angled end cut.

What the guide does

The work rests in the box while guide slots in its sides keep the saw on the chosen angle. The box is useful for mouldings, shaped strips of wood used for trim, picture frames, cabinet work and other repeated mitres where matching cuts matter. A mitre block does a similar job for small mouldings; a box gives more support when the moulding is larger.

When to use it

Use a box when several pieces need the same angle or when the stock is awkward to hold by eye. For a right-angled corner, the two meeting ends are commonly cut at forty-five degrees. If only one or two joints are needed, bevels, adjustable guides that mark an angle, may be quicker than making or setting up a box.

Cut and finish

Seat the moulding firmly against the bottom and side of the trough, then let the saw follow the guide slots. Leave a small finishing allowance when the fit needs to be tuned, and dress the end with a plane or a shooting board, a bench guide for trimming an end straight and true. Check the first piece against its mate before repeating the cut.

Know its limits

A standard box may not accommodate a deep or unusually long mitre. In that case mark the angle with a bevel and support the work by another method. A metal box is useful where its cost is justified, but protect it from damp because steel can rust. Accuracy is the reason to use a mitre box, so replace a worn guide slot before it allows the saw to wander.