They are used to shape and contour metal and can be used as an alternative to grinding wheels for removing weld deposits and slag. They remove metal slower and produce smaller sparks than grinding wheels. Flap disks are less robust than grinding wheels and can be damaged easily if care is not taken. Because they consist of only pieces of abrasive covered fabric glued to a solid backing by resin, there are fewer pieces that may become damaged and fly off so are generally safer than grinding wheels. They are lighter than grinding wheels so produce less vibration and are easier to operate.