This is a laplink tool. Laplinks are a specially made chain link that is split on one end and sprung open. You can use it for an expedient repair of a broken chain. You can slip the ends of the existing broken chain into the the link, and then with the pliers squeeze the link together, and it will hold reasonably well, without welding or forging---a great convenience for field repairs of tire chains. I wouldn't think that OSHA would approve of this sort of a field expedient repair on a chain that was going to be lifting something. You can also use the back side of the clamping pliers to spread a link if you want to take it apart. For more permanent repairs we have also been known to weld the lap some, something to do if you have problems with them spreading out over time.