A piercing saw is shaped like a smaller coping saw. The blade is held in tension in a metal frame.
Saw blades come in many different thicknesses and your blade selection will depend on the material being sawn and nature of the work being done. For very fine delicate work, and for cutting very thin material use a finer blade, and for general purpose cutting a heavier blade. Saw blades have a range of sizes, from finest to coarsest: 8/0, 7/0, 6/0, 5/0, 4/0, 3/0, 2/0, 1/0, 00, 0, 1, 2, 3, 4, 5, 6.
A piercing saw is often used with a V-board, also known as a birdsmouth board, which is a wooden board with a "V" shaped cutout in one end. In use, the V-board is clamped to the bench so that the section with the cutout hangs over the edge. This allows the work to be held down flat whilst shapes are cut into it. Either the work or the saw frame may be rotated. The V-cutout allows the saw blade to pass through the work unimpeded. When eventually worn or damaged, the board is easily replaced.