Rasps are steel tools with rows of sharp teeth used in both wood and stone carving. The purpose of a rasp is to smooth the wood or stone after the main shape of the sculpture has been defined. As you use this tool, the marks made by chisels and previous carving tools will disappear. Some files that have smoothing surfaces on both ends are also called riffler rasps. Most brands of rasps are numbered from 1 to 15, going from coarser to finer grain.

Step1 Select a coarse rasp to begin your smoothing. Wood carvers usually start with a finer grade than those carving in stone due to the softer texture of wood.

Step 2 Progress to finer-tooth rasps as you need to erase tooth marks from previous rasps and other tools.

Step 3 Select the size of rasp according to the size of your project. This means the length of the tool and blade and does not necessarily refer to the coarseness of the grade. For example, smoothing a small sculpture made of delicate alabaster will be much more effective with a small, thin rasp.

Step 4 Test out rasps with and without handles. Some rasps are made with handles and others are not. It is a matter of personal taste which you prefer to use.

Step 5 Choose a rasp that has a slightly convex blade--like an upside down spoon--to smooth a flat area of stone or wood. Many handmade rasps have a convex side. Machine manufactured tools tend to be more uniformly flat sided.

Step 6 Smooth out a corner area of your sculpture with a rasp whose teeth cover the very edge of the tool's surface. This task is harder to accomplish with a rasp that has a bare area without teeth.

Step 7 Experiment with tools that are curved and oval in addition to the straighter file-shaped rasps.