This is the Hasp and Hatch Puck-Style Guard Lock from Diversi-Tech, part number DT39002. The puck style lock is great because it completely covers your hatch and prevents thieves from finding anything to cut. It is perfect for the cam door lock found on many enclosed cargo trailers and Diversi-Tech guarantees this lock to be bolt cutter proof. To use the lock, the key into the lock cylinder, turn the key and the pin out of the way. Slip it over your hatch, push the lock back into place, turn the key, and you are ready to go. Here is a typical hasp and hatch that you might use this lock on. It fits over the hatch, and locks into place and there is nothing for a burglar to cut. And that does it for the Hasp and Hatch Puck-Style Guard Lock from Diversi-Tech, part number DT39002.