It has been common in school benches to affix it to a board, which rises considerably above the top of the bench, Fig.

169, but a better plan is to have the top of it no higher than the bench-top, Fig.166.Then the light on the bench is not obscured, and when a flat top is needed for large work it can readily be had by removing the tools.

Elaborate benches with lock drawers are also much used in the shops of large city schools.
[Illustration: Fig.168.A Rapid-Acting Vise.] _Vises_ for holding wood are of three general styles, (1) those with an upright wooden jaw, Fig.

167, which holds wide pieces of work well.
They are now made with an automatic adjusting device by which the jaw and the face of the bench are kept parallel; (2) wooden vises with a horizontal jaw, guided by parallel runners, Fig.

166, and, (3) metal rapid-acting vises, Fig.168.The latter are the most durable and in most respects more convenient.