Studsaver puts the thread back onto damaged bolts It is easy to use & fits many different thread sizes Attach the studsaver to the bolt shank close the jaws finger tight with the adjuster & then turn in the direction of the arrow Studsaver has two specially hardened steel blades which guided by the perfect thread path regroove the thread over the damaged area Also ideal for aluminium & plastic bolts UNCUNF 1434 Metric