One end is a very short drill bit, with a stop ring. It is precisely sized to engage the other end. That end is a hardened conical tap, designed to cut into the hole created by the stopped bit and jam before it bottoms out.

• Unscrew damaged screw heads.

Fall into three categories:

• Extractor only.

• Double ended extractor/pilot combo.

• Separate pilot drills.

• Always wear eye protection.

• Consider impact protection.