These are continually necessary to bind pieces of wood together till the glue has set in the joint. As will be seen from the illustration, Fig. 39, pressure is exerted by turning the two screws, the wood being held between the square jaws. They are made in various sizes, determined by the length of jaws. The nine-inch will probably be most useful to begin with, as there is comparatively little that cannot be done with them. If the screws work unpleasantly stiffly, a little soft soap and blacklead will be found a good lubricant. Oil should not be used, as both screws and jaws being of wood it would cause them to swell.
Fig. 39. - Hand-screws.