How to use: 1. Apply penetrating lubricant to the gap between broken bolts and female threads. 2. Place a prescription underhole at the center of a broken bolt or lacked bolt on a drill machine. 3. Apply a small amount of mechanical oil to the opened hole and screw the corresponding extractor into the left turn (counterclockw). 4. After the extractor cannot be tightened, please be careful not to break it in the counterclockwise direction, the broken screws will loosen and the broken bolts will come out from the female thread, so it will be completely removed. 5. Extracted bolts are scapped with pliers or vice, and screw the extractor into the clockwise direction.