Hi Lynne, you need to drill a pilot hole into the bolt or stud you are attempting to remove. This should be deep enough to get approx. 5mm of the screw extractor inserted into the thread. You put the extractor into a t-handle tap wrench or a socket that fits the square head. The extractor are left hand thread, so you turn them anticlockwise. Release agent or heat [sometimes both] may be required.