Hi Michael, you need to drill a pilot hole into the bolt or stud to allow the screw extractor to enter approx. 4-5mm into the thread. You need a tap wrench or Amtech ratchet tap s1450 or s1460 depending on the size extractor you are using. The extractors are used anti-clockwise. Additional heat and/or release fluid may also be required. Do not force the extractor taps to much as they can break.