A knife thread insert is a type of thread insert fastener that has honed threads for easily slicing and biting into wood for greater holding. Typically made of brass, these threaded inserts for wood or plastic also have a slot to accommodate a screwdriver blade. Stainless steel versions work well for insertion into metal. Items vary by internal thread size, length, and other considerations. For more on inserts, see our self locking inserts, key locking inserts, and press inserts.