Flap discs are made with layered flaps mounted on a rigid backing. New abrasive is exposed as the flaps wear away. Flap discs grind and cut material and finish the surface in one step. They come in two shapes: Type 27 (flat) and Type 29 (angled). Interleaf flap discs alternate non-woven nylon flaps with cloth-backed coated flaps and are used for finer finishing and polishing.