The Keyhole Saw
The compass, or keyhole, saw bears a narrow, tapered blade in order for it to fit into narrow spaces. Some types come with three or four alternative blades that can be replaced to meet the demands of the particular cut: there could be ripsaw blades and blades for crosscut work. Due to its flexibility, the compass saw is especially useful for cutting along curved lines. This saw is also frequently used for short cuts, or to finish off a long cut and for fine irregular sawing.
The coping saw is a small tool, a saw blade carried in a steel frame. It is occasionally called a jig saw. The blade can be removed and can range in thickness from athreadlike wire to 1/8-inch. width. The blade is thus fragile and must be used only on thin wood. When an interior cut must be made, a hole is bored, and the blade is threaded through the hole and then connected to the frame. On the frame are pawls with slots where the blade fits. Typically the blade can turn inside the frame. Blades may be flat or spiral: the spiral blade has the advantage of being able to cut in whatever direction without turning. For vise work, the teeth of the coping saw must point toward the handle, but on work held by a saw horse, it is best to have the points turned away from the handle.