Best Rated Trailer Coupler Lock

Last Updated on December 6, 2021

If you tow horses, you know how valuable a horse trailer is. You will do anything to ensure that your trailer is safe from thieves. Best trailer coupler locks give you the peace of mind that your trailer is well protected. 

Coupler locks are designed to keep the coupler securely attached to the lock, so no one can pull up and drive away with your trailer. They are simple to use and ensure your trailer will be kept safe. Trailers are expensive pieces of equipment, so having a lock is a good idea, as many thieves target trailers.

For those who do tow horses, it is important to keep your horse trailer safe. Many people have valuable equipment stored in their horse trailer, let alone the value of the trailer itself. It is important to keep your horse trailer protected from robbers, as you don’t want your horses to become stranded away from home.

How To Choose the Best Trailer Coupler Locks for Your Trailer – What You Have to Consider

When choosing a coupler lock for your trailer, there are several things you want to take into consideration. Most importantly, you will want to make sure the coupler lock you selected will fit your trailer. Some coupler locks are designed to be adjustable, which is great if you tow different trailers.

How To Choose the Best Trailer Coupler Locks for Your Trailer - What You Have to Consider

Coupler locks are great because they are designed to be easy to put on your trailer. They are locked and unlocked with one key. They are designed to hold up against lock picking mechanisms.

If you are worried about someone stealing your trailer, a coupler lock is an easy and effective way to protect your trailer. Most coupler locks range from $25-$50, so you won’t have to spend a fortune to get a good lock.

What are the Advantages/Benefits of the Best Trailer Coupler Locks?

Having a coupler lock is great to have if you travel to lots of places. It is easy to transport and simple to put on your trailer hitch. They hold up against lock picks and most lock breaking mechanisms. They are heavy duty and give you peace of mind.

They are easy to lock and unlock. Coupler locks are generally reasonably priced, making it well worth the investment. They are generally made from forged steel.

What’s the Best Way to Use This Product?

Coupler locks are best used to protect trailers when they are not being towed. They prevent people from backing up and hooking your trailer to their truck. They are best used for horse, stock, camping, boat and storage trailers.

When you are not using your trailer, simply put the coupler lock on the coupler of your trailer and lock it. The coupler lock works like a trailer ball and then locks into place on the coupler, keeping your trailer safe. Make sure to keep hold of your key, as getting a coupler lock off if you lost your key is a hassle.

If you are unsure how to use a coupler lock, there are tutorials to help you understand how to properly secure your coupler lock to your trailer. Once you get the hang of it, you’ll appreciate how easy they are to use.

Prerequisites to Using the Product

Before using this product, you want to make sure the coupler lock you buy will fit your trailer. Though most coupler locks are adjustable, not all of them are. You’ll want to know what the size of your coupler in order to find a lock that will fit properly.

 Since trailers are generally stored outdoors, the locks are prone to freeze in cold temperatures. It is a good idea to keep some de-icer handy, so you are not stuck with a frozen lock. If your trailer is not parked under a cover, you’ll want to get a lock that can hold up against weather conditions, especially rain.

There are several coupler locks available that hold up against rust and corrosion. If you live in a climate with harsh weather conditions, you will want to have a weather-resistant lock. A weatherproof lock will hold up in tough conditions, so you don’t have to worry about your lock rusting and weakening.

Though coupler locks work great at protecting your trailer from thieves, a determined thief with the right tools can get most locks off. That being said, your trailer is still safer with the lock on, as it takes a lot of work and heavy-duty tools to get coupler locks off.


Best Trailer Coupler Locks

Master Lock Universal

The Master Lock Universal coupler lock is designed to fit hitch sizes 1-⅞ inch, 2-inch, and 2-5/16 inch. Its sturdy design will keep your trailer safe. It is easy to use and will allow you to rest assured that your trailer is secure.


  • This lock fits several sizes of hitches.
  • It is easy to install and remove.
  • It holds up against rust and corrosion.
  • Its bright red color discourages thieves.
  • It resists picking and prying.
  • Two keys are included with the lock.


  • Though it does hold up well, it can’t stop all determined thieves with the right supplies.

Master Lock Universal

Trimax UMAX100 Premium Universal ‘Solid Hardened Steel’ Trailer Lock

The Trimax UMAX100 Premium Universal is designed to fit all sizes of trailers. Its heavy-duty build includes a dual ratchet lock system. Its weather-resistant design, along with its keyhole cover keeps dirt and water out.


  • The locks hardened steel design keeps thieves away.
  •  It can work with any size hitch, making it versatile.
  • It is easy to use.
  • It holds up well in rainy and muddy weather conditions.


  •  A determined thief with the right tools could break it.
  • Though it is designed to fit all sizes, it does not always snuggly fit.
  • The plastic casing, unlike steel, does not hold up well in tough conditions.

Trimax UMAX100 Premium Universal 'Solid Hardened Steel' Trailer Lock

Master Lock 377KA Trailer Hitch Lock

The Master Lock 377KA Trailer Hitch Lock is designed to fit 1-7/8 inch, 2-inch, and most 2-5/16 inch in trailer hitches. It works effectively with vehicles, trailers, and RVs. Its zinc construction is durable and holds up against rust and corrosion.


  • This lock fits most trailers.
  • It holds up well in tough conditions.
  • The zinc construction is heavy-duty.


  • A well-equipped thief can break this lock.
  • The locks are all keyed the same.

Master Lock 377KA Trailer Hitch Lock

Tow Ready (63228) ‘Gorilla Guard’ Coupler Lock for 2″ Couplers

The Tow Ready Gorilla Guard Coupler Lock is a well-made lock, designed to shield against tampering devices. It fits most two-inch couplers. It gives you the peace of mind that your trailer is secure from thieves.


  •  It is heavy duty and holds up against tampering.
  • The lock is easy to use.
  •  It is difficult to cut, making it safe from thieves.


  • It does not fit all trailer sizes.
  • A very determined crook with heavy-duty equipment could break it.
  •  It’s limited by the coupler (including lip), as it cannot exceed 3-13/16 inches and the height of coupler lip, as it cannot be greater than 5/16 inches.

Tow Ready (63228) 'Gorilla Guard' Coupler Lock for 2" Couplers

 Blaylock TL-33 Coupler Lock

This Blaylock TL-33 Coupler Lock is a high-quality lock designed to fit most trailers. It is constructed from durable aircraft-grade aluminum and Its tough design is made to keep greedy thieves away. It is a lightweight lock that gives off a beefy look.


  • This coupler lock is intended to fit over 30 different coupler style brands, including recreational and commercial trailers.
  • The high-quality aluminum holds up against wear.
  • It is easy to use.
  • It holds up against rough weather conditions.
  • You can use whatever lock you want with it.


  • Though unlikely, a determined thief with the right tools could break it.

 Blaylock TL-33 Coupler Lock

The Best Trailer Coupler Lock Available

All of these coupler locks for your trailer are top quality and will keep your trailer safe. You can rest assured that these coupler locks will keep your trailer secure from thieves.

Though all these trailer locks are great, the Master Lock Universal stands out above the rest. It is affordable, durable and easy to use. Unlike the other locks, it has a bright red color to help discourage thieves. Check the following post to learn more about the other ways to lock a trailer for horses.

This lock is made from durable steel, making it difficult for robbers to mess with. It is easy to put on your trailer and comes with two keys, giving you a spare in case you lose one. Unlike the Gorilla Guard and Master Lock 377KA Trailer Hitch Lock, it is designed for the majority of trailers.

This coupler lock holds up against rust and corrosion. It is engineered with an advanced locking mechanism, making it hard for thieves to pick and pry. It comes at a great price that won’t break the bank.

Though all of these are great coupler trailer locks, it is important to remember that a determined thief can find a way to break the lock with the right tools. However, these locks still work as great protection and are a good idea to have. Having a coupler lock on your trailer can give you peace of mind.


Who invented the trailer coupler lock?

It is said that the trailer coupler lock was invented by Byrel Leigh "B. L." McPhail, an employee of the Yellow Freight System, Inc. (now YRC Worldwide) in Boulder City, Nevada. He was not given credit for it at first, but later the company awarded him a patent for it.
The purpose of the invention was to prevent trailers from being accidentally uncoupled. McPhail designed a locking device that would fit over the coupling head and lock it, preventing the coupler from releasing. McPhail also invented other devices for use with trailers, such as a hydraulic brake assist and a hydraulic lift axle.
An invention of such impact was the result of an accident in which McPhail's truck separated from the trailer while on the road and got hit by another vehicle. In the accident he lost several teeth and injured his eyes. While he was recovering from surgery, he had time to think about how he could have prevented the accident.
The trailer coupler lock was patented in 1967 and is still in use today. While there are many different types of trailer locks available on the market, the McPhail lock is one of the most common.

How does the coupler lock mechanism work?

The trailer coupler lock is mounted on the head of the kingpin, which is located in the middle of the two semi-trailers. It has a mechanism that locks onto one of the slots at the end of each side rail of a fifth wheel, preventing it from coming apart and separating from the semi-trailer.
When the lock is unlocked, it slides up and down easily over the kingpin. After locking, however, it becomes extremely difficult to slide off due to the shape of the chamber mechanism.
The coupler lock has a large metal chamber that houses a spring-loaded plunger. The plunger fits into a small hole in the end of the kingpin. When the lock is in the unlocked position, the plunger is pushed down by the spring, which allows it to slide over the kingpin.
When the lock is locked, the plunger is pushed up into the chamber, which blocks the hole in the kingpin and prevents it from coming out. This holds the trailers together and keeps them from accidentally separating.

What types of trailer coupler locks are on the market?

There are several different types of trailer coupler locks. In addition to the McPhail lock, there is the wedge lock and the latch lock. The wedge and latch locks work in a similar fashion, with the difference being in which side rail they fit on.
The wedge lock fits into the side rail on the truck, while the latch lock fits into the side rail on the trailer.
The most common type of lock is the McPhail lock, which fits over the head of the kingpin and locks onto one of the slots at the end of each side rail.
Another type, the Dee Zee DZ433, features a rotating steel bar with notches and a keyed cylinder lock with dual locking levers.