Snap-on is an English term referring to a quick-release system for replacing presser feet. A presser foot is a machine part that holds the fabric in place under the needle during sewing. Because different types of feet are used for various sewing techniques, such as attaching elastic or decorative gathering, they need to be changed. With the Snap-on system, no tool, such as a screwdriver, is needed for replacement. The existing foot is released by pressing a button or a small lever on the foot holder, causing it to fall off. The new foot is then simply placed on the needle plate, and by lowering the holder, it automatically "clicks" into place.