The way they work is you remove the rear bolt, insert a small flat head screw driver, wind it back, and then bold it in without removing the small screw driver allowing the tensioner to extend prematurely. Make sure you don't move the bike when the tensioner is out, and after the new one is in its a good idea to put the bike in 5th gear and push it forward a foot or so to make sure the tension is fully extended before starting the bike.