Skip to main content

The following review has the purpose to inform the reader about the topic of anti-theft devices for trailers of motor vehicles. Within the scope of the same, it shall be shown which possibilities there are with regard to securing the trailer against theft and how they work. Furthermore, an interesting look at the advantages and disadvantages of the same will be given, as well as some tips for the purchase of a trailer security.

The most important facts in brief

  • Trailer locks are an essential measure against trailer theft and can be found in three different variants.
  • There is a basic distinction between trailer locks with low, medium, and high protection against theft.
  • Although there are other variants for theft protection, trailer locks are the most common method to protect against thieves.

What is a trailer hitch lock?

Many trailers designed and built for cars already have an anti-theft device in the form of a plug-in lock. However, this can be cracked in no time by criminals with little experience. Accordingly, the plug-in lock only provides a low level of protection for the trailer against access by third parties. The so-called box lock provides medium protection of the trailer against theft.

This security device is put over the coupling of the trailer and thus prevents the manipulation of the connection between the trailer and the trailer coupling of the car.

On the other hand, the best protection for the trailer is provided by certified trailer locks, which are manufactured exclusively with high-quality materials and make life difficult even for real professional thieves.

Another interesting way to protect the trailer from thieves is to equip its wheels with a wheel claw as soon as it is parked somewhere. The next paragraph will briefly describe how the locks or anti-theft devices work.

How does a trailer hitch lock protect against theft?

In principle, the function of all locks can be determined equally. The lock has the task of protecting the object from unauthorized persons.
Since a trailer, because of its size, can not be easily moved from the spot and usually requires a car for this, a lock is used, which breaks the connection from the trailer to the car.

The purpose behind the lock is that you can no longer connect a vehicle to the trailer without removing the lock in front of it.

An ordinary mortise lock and the trailer’s integrated lock system can be picked relatively easily and with little experience. This requires simple bolt cutters, which are highly likely to be used by any trailer thief.

However, there is another function that a trailer lock has to protect against theft. The lock has the property to serve as a deterrent.

What types of trailer locks are there and which one is right for you?

If you want to buy a trailer lock, you have the choice between three types:

  • Simple trailer locks.
  • Medium security trailer locks.
  • Certified trailer locks.

The simple trailer locks are plug-in locks that are usually added after the purchase of a trailer. The medium-security trailer locks are basically the box locks which are a very popular purchase among trailer owners because of a good price-performance ratio. Certified trailer locks are the last option and are often only custom-made. Depending on how you want to use your trailer lock, a different type is suitable.

Trailer Hitch Lock – Best Choice

Best choice

REESE Towpower Universal Coupler Lock

The Reese Towpower Universal Coupler Lock is built strong and designed to fit 1-⅞”, 2”, and 2-5/16”couplers. Its bright, highly visible yellow color guards against truck and trailer theft while its premium lock resists picking, prying and drill outs giving you peace of mind.

  • 4,6 Rating
  • Advanced lock resists picking, prying and drill outs.
  • Dimensions: 9” x 9” x 3”.

Best Trailer Hitch Locks on the market:


Rhino USA Trailer Hitch Lock


  • Rating: 4,7 ∗∗∗∗∗
  • Weatherproof Anti-Theft Lockable Pin.
  • For Hitches Class III, IV.


Trimax UMAX100 Premium Universal Dual Purpose Coupler Lock


  • Rating: 4,7 ∗∗∗∗∗
  • Size fits all (from 1-7/8″, 2″, to 2-5/16″, all coupler types).
  • Provides 360 degrees of hardened steel protection.


CURT Powder-Coated Aluminum Trailer Tongue Lock


  • Rating: 4,6 ∗∗∗∗∗
  • Fits most 2-5/16-inch and some 2-inch flat and rolled-lip trailer couplers.
  • Highly corrosion-resistant aluminum construction.


Tow Ready Gorilla Guard Coupler Lock


  • Rating: 4,8 ∗∗∗∗∗
  • Fits most 2-inch trailer couplers.
  • Protects Unattended Trailers.

What are the advantages and disadvantages of a simple plug-in lock?

A simple plug lock is, as the name suggests, pushed (plugged) into a locking channel of the trailer hitch and then locked with an associated key.

The advantage of the plug lock is that it is very easy to use. It is also very easy to stow away. With the size of a key, it is very easy to store in the glove compartment.


  • Easy to use.
  • Easy to stow away.
  • Inexpensive.


  • Easy to crack.
  • Easily unmissable and therefore no high deterrent effect.

What distinguishes a box lock, and what are its advantages and disadvantages?

Box locks have a very distinctive appearance. Due to the box-like construction of the lock, these not only protect the entire hitch of the trailer but also have a high ability to deter thieves. The box made of steel is difficult to store in the vehicle because of its size and may cause inconvenience while driving.


  • Good price-performance ratio.
  • Protects from damage.
  • High deterrent effect.


  • Unhandy.
  • Difficult to install.

Another disadvantage is that a box lock is difficult to handle. Since the housing is relatively massive, the installation does not always succeed with ease. For campers and trailer owners who are definitely in a hurry, this can be their undoing.

Advantageous is the stability, the housing consisting of the hardened steel. This makes the lock much harder to pick than a simple mortise lock and can not be removed with a simple hammer, for example.

Relate: Tires for RVs & Motor Homes


Purchase criteria

Below, we will show you which aspects you can use to decide between the multitude of possible trailer locks.

The criteria with the help of which you can compare the anti-theft device for trailers include:

  • Material.
  • Size.


This criterion is very important when choosing a trailer lock, as it directly contributes to the safety and protection of the trailer.

You should definitely be aware that simple socket locks are mostly made with cast iron. Cast iron is relatively unstable and can be easily broken. Therefore, look to find a lock with harder metal, such as brass.

Also, it is very important that you examine the keys to the lock before you buy.

If they look too small or fragile, you should be aware that these keys could break very easily. In the worst case, you would have to break the lock with tools or a drill.

Box locks generally deal with hardened steel. Make sure with your manufacturer that it is indeed hardened steel and not a fragile substitution. Very important to note with box locks is the quality of the weld. If you find any irregularities, it can cause the lock to break very easily.


Since there are different variants of trailer locks, there will also be correspondingly different sizes regarding the locks.

First, you should be aware of which variant of the lock suits you best.

Since most manufacturers build an integrated socket lock into their trailers, in this case the size of the lock is similar everywhere. Still, check out the compatibility with your trailer.

For box locks, the size may differ depending on the manufacturer.

However, it is very important that you measure the length, width, and height of your trailer hitch before buying and then come to a conclusion.

In some cases, the certified trailer locks are similar to the box lock. However, there are manufacturers that make custom locks. Often the size then corresponds with the individual design of the manufacturer.


For every owner of a trailer, it makes sense to think about the purchase of an anti-theft device. This way, you can sleep soundly at night, as the security of the trailer against theft is significantly increased. Already the deterrent potential contributes a lot. Before making a purchase, it is important to know exactly which model the anti-theft device is intended for. Also, attention should be paid to the materials and their processing.

How to install the "UMAX100" Universal Unattended Coupler Locks by TRIMAX - Video

Max Welder (rvneeded)

Max Welder (rvneeded)

Max Welder is a mechanic enthusiast. Currently, working at a small company. Experienced in electronics, car tools, and security systems. In his spare time, he writes articles for various blogs.

Leave a Reply