Master Lock Trailer Coupler Lock

The 379ATPY coupler lock is built as a universal fit for 1-7/8 in (48mm), 2 in (51mm) and most 2-5/16 in (59mm) couplers, so a 2-5/16 coupler is covered on most trailers. It is one lock that spans all three of the common ball sizes, which is why it works if you run a mixed trailer fleet with different coupler sizes.

Yes. The 379ATPY uses a rekeyable cylinder for keyed alike convenience, so a fleet of them can be brought onto a single key rather than handing a driver a ring of keys. That is the practical reason a property manager or contractor buys more than one at a time.

A coupler lock like the 379ATPY blocks the coupler itself, so a thief cannot drop the trailer onto a ball. That is the theft path when the trailer is parked unhitched. A hitch pin lock solves a different problem, securing the ball mount in the receiver on the tow vehicle. If the trailer sits unattended in a lot or yard, the coupler lock is the one that matters.

It is built to resist rust and corrosion, and Master Lock lists it for marine and offshore security as well as trailers, trucks and towing. Boat trailers at a ramp and equipment trailers parked outdoors are the intended duty.

Easy on, easy off is the design point. It installs and removes without tools, so a crew moving trailers several times a day is not fighting the lock at every stop. The locking mechanism resists picking and prying, so the quick handling does not come at the cost of the security.