mudhut

No. It fits into the pulley and holds the inside. When you look at the pulley, there is a balancing mass that goes part the way round the inside. The aluminium block on the tool fits into the rest of the pulley (where the balancing mass isn't) so when you try to undo the nut, the crankshaft rotates until the mass on the puley hits the aluminiun block, holding the crankshaft against the rotation of the nut.