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Master Lock

Master Lock Black Universal Size Trailer Hitch Lock, Trailer Coupler Lock for Securing RV’s, Horse Trailers, Tool Trailers and More, 379ATPY

  • Based on 5,937 reviews
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Availability: In Stock.
Fulfilled by Amazon
Arrives Wednesday, Jul 1
Order within 21 hours and 34 minutes
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Style: Trailer Hitch Lock


Features

  • Trailer hitch lock fits 1-7/8 in. (48mm), 2 in. (51mm) and most 2-5/16 in. (59mm) trailer couplers
  • Trailer lock is best used for vehicles, trailers, and RVs
  • Trailer coupler lock features advanced locking mechanism to resist picking and prying
  • Trailer hitch lock is constructed from zinc to resist rust and corrosion
  • Includes one trailer coupler lock, two keys

Description

The Master Lock 379ATPY features a universal trailer coupler lock, designed to fit 1-7/8 in. (48 mm), 2 in. (51 mm) and most 2-5/16 in. (59 mm) couplers. The advanced locking mechanism provides resistance to picking and prying. The Limited Lifetime Warranty provides peace of mind from a brand you can trust.

Brand: Master Lock


Special Feature: Portable


Lock Type: Key Lock


Item dimensions L x W x H: 5.1 x 3.5 x 4.6 inches


Material: Zinc


Brand Name: Master Lock


Recommended Uses For Product: vehicles, trailers, RVs


Number of Pieces: 1


Included Components: Unit^Instruction Guide


Model Number: 379ATPY


UPC: 071649229220


Model Name: Universal Towing Coupler Lock, Steel


Global Trade Identification Number: 20


Manufacturer Warranty Description: 1 year manufacturer


Manufacturer: Master Lock


Unit Count: 1.0 Count


Manufacturer Part Number: 379ATPY


Item Type Name: Universal Trailer Hitch Lock


Additional Features: Portable


Lock Type: Key Lock


Controller Type: Hand Control


Control Method: Touch


Smart Home Compatibility: Not Smart Home Compatible


Style Name: Trailer Hitch Lock


Color: Black


Shape: Rectangular


Material Type: Zinc


Finish Types: Polished


Item Dimensions: 5.1 x 3.5 x 4.6 inches


Item Weight: 16 ounces


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Wednesday, Jul 1

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Similar Products

Top Amazon Reviews

    • Solid, Simple Trailer Hitch Lock That Adds Real Peace of Mind
Style: Trailer Hitch Lock
The Master Lock 379ATPY universal trailer hitch lock is a straightforward, effective security solution that does exactly what it’s meant to do. If you’re looking for an easy way to secure a trailer without overthinking the setup, this lock delivers dependable protection with minimal hassle. Fit and compatibility are strong points. The universal design works well across different types of trailers, including RVs, utility trailers, horse trailers, and tool trailers. It fits securely over the coupler and blocks it effectively, preventing anyone from hitching up and towing off your trailer. Once installed, it’s very clear the trailer isn’t going anywhere. Build quality feels solid. The lock has a good weight to it and doesn’t feel thin or easily defeated. While no lock is completely theft-proof, this one is sturdy enough to act as a strong deterrent. It sends a clear message that the trailer is protected and not an easy target, which is often half the battle when it comes to theft prevention. Installation is quick and simple. You don’t need tools or complicated adjustments. It slides into place easily and locks securely. Removing it is just as easy when you’re ready to use the trailer, which makes it convenient for regular use without becoming annoying. The locking mechanism works smoothly. The key turns cleanly without sticking, and the lock opens and closes without feeling gritty or cheap. That’s important for something that may sit outdoors and be exposed to weather. So far, it’s held up well without signs of binding or corrosion. The black finish keeps it discreet while still looking tough and purposeful. It doesn’t draw unnecessary attention, but it’s obvious enough to let would-be thieves know the trailer is secured. It also looks clean and professional, whether the trailer is parked at home, a storage lot, or a campsite. Overall, this Master Lock trailer coupler lock is a reliable, easy-to-use security accessory that does its job well. Strong fit, solid construction, simple operation, and broad compatibility make it a smart choice for protecting trailers of all kinds. If you want added peace of mind without complexity, this is an easy five-star product. ... show more
Reviewed in the United States on December 15, 2025 by The country charm
    • Solid Protection ,Total Peace of Mind!
Style: Trailer Hitch Lock
This Master Lock is an excellent product. It feels heavy-duty and secure, giving me way more confidence when I leave my RV at the campsite or in storage. The universal fit worked perfectly on my trailer coupler, and the black finish looks sleek while being weather-resistant. A small price to pay for such great security! ... show more
Reviewed in the United States on March 17, 2026 by William B
    • Perfect Fit and Great Peace of Mind
Style: Trailer Hitch Lock
This Master Lock fits my trailer perfectly and feels very secure. It was easy to install and solidly built. Once it’s on, I feel confident that it will help prevent my trailer from being stolen. Definitely gives me peace of mind and I would recommend it to anyone looking for a reliable trailer lock.
Reviewed in the United States on December 17, 2025 by Shannon Penna
    • Great trailer hitch lock!
Style: Trailer Hitch Lock
My son picked out this trailer hitch lock and says it is very sturdy and should do the job with no problems.
Reviewed in the United States on August 24, 2025 by Tulsa Walker
    • Snug Fit
Style: Trailer Hitch Lock
Interesting assembly. Fits snugly around the hitch.
Reviewed in the United States on May 23, 2026 by SVB
    • Master Lock Trailer Coupler Lock 379ATPY - Fits 1-7/8", 2", 2-5/16"
Style: Trailer Hitch Lock
I needed some locks for heavy-duty trailers that use 2-5/16" Bulldog couplers. I had previously had bad luck with Guardian locks, which were more expensive, not as well made, and not backed up by the manufacturer. These Master Lock coupler locks not only appear to be much better than the Guardian locks, they come with a limited lifetime warranty from Master. This lock fits the 2-5/16" Bulldog/Hammerblow couplers (in spite of the fact that this size is not listed) and is a very reasonable price. Fortunately, I cannot say how well they resist thieves' attempts to steal the trailer, but they will certainly provide a substantial deterrent. I bought mine in October 2008 and they have a chrome finish that appears to be excellent. Despite being in the weather all winter in Indiana, they still look and operate as if they were brand new. It looks like Master Lock has switched to the pictured painted or powdercoated finish instead of the chrome plating. I don't know how well the new finish will protect the mechanism compared to my chrome ones, but keep in mind that Master Lock offers a lifetime warranty, which covers operation but not finish. I have never had any trouble installing the lock to the coupler, but I agree that it can be a bit loose when locked. The lock attaches via a number of notches and it's unlikely that you'll find one that is exactly tight. There's no ratchet to help you with this, so you must squeeze the locking mechanism as you turn the key. It's more trouble to write about it than to do it. In spite of the slight looseness, I think someone would have a tough time getting it off the coupler. Regarding sticking tumblers or locking mechanism, I find that I must lubricate all my locks, including these, occasionally. Amazon also sells Master Lock model 379DAT, which has a rubberized coating. I bought one of those recently. It seems to be a bit looser on the coupler, I think because of the coating. Unless you are concerned about the possibility of the coupler's paint chipping from metal-to-metal contact, I would recommend the model 379ATPY over the 379DAT. See Painter Bill's review, dated July 11, 2011. Both of these locks are highly recommended, but especially the 379ATPY. ... show more
Reviewed in the United States on January 2, 2012 by Loren
    • Master Lock
Style: Trailer Hitch Lock
Works as Advertised
Reviewed in the United States on May 11, 2026 by Trey
    • good merchandice
Style: Trailer Hitch Lock
They work great
Reviewed in the United States on May 2, 2026 by michael t warner

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