Flap wheels install in bench grinders, pedestal grinders, die grinders, or other rotary tool to debur, smooth, and polish surfaces. Flap wheels smooth on the side of the wheel rather than the face, making them a good choice for edges, flat surfaces, and hard-to-reach areas such as the inside of pipes and tubes. Overlapping flaps exposes fresh abrasive as the abrasive wears away. Mounted flap wheels have an integrated spindle (or shank) that attaches the wheel to the tool. Unmounted flap wheels have an open center to attach the wheel to a mandrel.