General purpose files shape, smooth, and sharpen metal. They remove material in applications that don't require a file optimized for aluminum. These American-pattern files abrade material more aggressively than Swiss-pattern files used for precision filing and finer finishes. Rectangular files perform general filing and abrade material from flat surfaces and linear edges. Half-round files have a flat face to abrade material from rounded grooves, holes, and edges. Round files smooth or enlarge holes, circular openings, and concave surfaces. Triangular files clean up square corners and angles less than 90°, create V-grooves with 60° angles, and start the process of squaring round holes. Square files abrade material in square or rectangular slots, grooves, and keyways. Knife-edge files cut or smooth keyways, narrow slots, V-grooves, and tight angles. Warding files debur and repair keyholes, cut ward notches in keys, and refine narrow slots.