A surform rasp is a very coarse rasp, much like a food grater, which has a cutting surface made of expanded metal. It allows small particles of material to pass through it without clogging its cutting teeth. Surforms are available in a number of sizes and shapes, both flat and curved, and usually come with replaceable blades.
A surform is very effective for trimming, shaving, sculpting, and removing large quantities of material, including wood, plaster, clay, foam, and some plastics. It leaves a rough finish that usually requires additional sanding. When using a surform with a very soft substance, such as foam, care must be taken to avoid tearing out large chunks of material.