This is a simple to use lock. It is intended for trigger style coupler latches, like this. You see about a half inch span at the most. What this does is the key goes through there, like any other lock, and the pin comes apart. You slide through the latch, push the pin back in and there you are. It is simply installed and your coupler will not come off the ball. There you have it for part # 605DAT, the MasterLock solid brass coupler lock.