Removing or installing Shimano Cranks? You’ll most likely need one of these. 

If removing cranks, loosen the two pinch bolts and then use this tool to unscrew the plastic preload screw so you can take the cranks off. 

If fitting cranks, tighten the preload screw using this tool and then tighten the two crank bolts. Be careful to nip the preload screw up somewhat gently, that’s why this tool doesn’t have anywhere to grip with a spanner/allen key.