The
combination square is a steel tool 12" long with a 4½" handle. The blade
is either slotted or grooved. The blade and handle are fitted together to allow
the cutting of 45° or 90° angles. It is useful for marking short measures and
also has a spirit level built into the handle. In addition to making 45° and 90°
angle cuts, the combination square can be used for measuring depths and scribing
lines a given distance from the edge of a board. Special attachments are
available but are not normally used by the carpenter. The most common of these
are the centering head and the protractor head.