A keyhole saw is a fine-toothed handsaw, with a long, narrow, tapered blade. Keyhole saws, also called pad saws or jab saws, are used mostly for cutting tight curves and, by first drilling a pilot hole, closed inside cuts, in materials such as wood, hardboard, plastic, and metal. They work well for making openings for pipes and electrical boxes, and almost any straight or curved internal cuts that are too large for an auger bit, a drill, or a hole saw. Because keyhole saws cut on the pull stroke and have very sharp teeth, they make clean cuts even in hard-to-get-at areas.
Keyhole saw blades are typically 10" to 12" long. They may be fixed or retractable. Keyhole saws with fixed blades are the more common and less expensive type. The retractable blade variety usually have a cast iron handle or, in some cases, a wooden handle. The ability to retract the blade to an optimum length helps prevent unwanted flex to the blade should the full length of the blade be obstructed in some way. A quality keyhole saw has removable blades with a variety of tooth spacings for cutting different materials.
With the advance of specialized building methods and materials, designs specific to these trades have been developed. For example, one type of keyhole saw has a sharpened point at the tip of the blade, which can be pushed or jabbed through soft materials such as drywall without pre-drilling a hole for the blade.
Two power tools that do essentially the same job as a keyhole saw, but which work more quickly and with less effort, are the jig saw and the spiral saw.