Hi I'm new to these forums and I'm not quite sure if this was asked or even where to look to find it. The plastic pulley that comes with these kits to secure it on one side has a nut and on the other has what appears to be a flat screwdriver head. Logic says to find a small flat screwdriver to put into the screw side to keep it from turning to tighten the chain. I've tried 3 flat heads so far is it a flat head or a special tool? Reason for asking is because i bought my bike already put together with the kit.