Description You just need an adjustable spanner or a 5/8 or 16mm spanner, then: 1. Remove the bolt in the crank arm. 2. Screw the lower black part of the tool into the crank until tight. 3. Screw in and continue to tighten the silver piece of the tool until the crank starts to move. It is perfect for any home bike mechanic. Suitable for square tapered crank sets. Helps you get out of troubles fast. Practical and more convenient.