Redneck Trailer Supplies

RTS 101: Jacks, Couplers, & Locks

RTS 101 provides basic trailer parts information for the DIYer or for the business owner. For more information, please call Redneck Trailer Supplies toll free at (877) 9 REDNECK (973-3632).

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What types of trailer couplers are available?

We offer two types of trailer couplers, including a bumper pull (coupler clamps onto a hitch ball at rear of vehicle) and a gooseneck coupler (a pipe or square tube with ball coupling, clamps onto hitch ball mounted in the bed of a truck positioned above the rear axle).

What types of bumper pull couplers are available?

Straight tongue


Adjustable tongue

Flat mount

All are available in both stamped and cast coupler designs.

What is the difference between a stamped and cast coupler?

A stamped coupler is formed from high alloy sheet steel and the coupling head is integrated into the coupler body. This is a method of producing couplers that are not as durable as a cast coupler, but typically cost less. 

A cast coupler has a cast or forged coupler head that clamps onto the hitch ball. This provides for increased wear and durability as compared to a stamped coupler design. Cast couplers are typically more expensive than stamped couplers, but typically provide greater durability and longevity.

What is a straight tongue coupler?

A straight tongue coupler is typically used on smaller trailers that have a straight tube or channel extending from the front of the trailer. These couplers are typically bolted on, although weld-on versions are also available.  

The standard ball size for straight line couplers is usually 1 7/8” and 2”. However, there are some 2 5/16” models available. Weight capacity for straight tongue couplers typically range from 3,500 – 12,500 lbs.

What is an A-frame coupler?

An A-frame coupler is used on trailers with a triangle or “A” frame trailer tongue. These couplers are typically welded to the trailer frame. 

A-frame couples are designed for multiple types of trailers using either a 2” or 2 5/16” ball size. Weight capacity for A-frame couplers typically range from 5,000 – 15,000 lbs.

What is an adjustable tongue coupler?

An adjustable tongue coupler is used with a channel that welds to the trailer tongue. It can be raised or lowered on the channel mount depending on what height you may need to ensure level towing of your trailer. 

Adjustable tongue couplers are available in 2” and 2 5/16” ball sizes, and typical weight capacity ranges from 7,000 – 20,000 lbs.

What is a flat mount coupler?

A flat mount coupler typically mounts to a flat metal plate that is welded to the frame of the trailer. Flat mount couplers are most often used as an alternative to tow rings, more often in reference to pintle/drawbar eyes used on heavy trailers.  

The typical weight range for a flat mount coupler is from 14,000 – 25,000 lbs.

What kind of latching mechanisms exist for bumper pull trailers?

There are 4 main types:

Trigger style: This style allows for fast and easy locking and unlocking by simply pulling the trigger to latch or to unhitch. This type of latch also affords you the ability to adjust the locknut beneath the coupler for increased tension on the trailer ball.

Thumb style: This style allows you to press the latch handle back with your thumb. You can then place your coupler over the ball and push the latch down and forward to lock.

Yoke style: With this style you lift the latch and pull backward, raising the yoke over the coupler nose. To hitch, you must place the coupler on the ball and push the latch handle forward until the yoke drops over the nose.

Collar/pin style: With this style mechanism, one opens by pulling the retainer pin out, then pulling the spring loaded collar to the open position. To close, you position the latching mechanism over the hitch ball, close the hinged portion of the coupler, and then release the collar and insert the retainer pin. (This is a common latch design for most cast couplers.)

What is the difference between the 4B8 and the 4B8L Bulldog® collar-lok cast coupler?

The high-profile mechanism provides a larger handle/grip for easier latch operation, while the low-profile latch is less susceptible to damage in the field. The selection of high-profile latch (4B8) versus low-profile latch (4B8L) for the Bulldog® Collar-Lok coupler is based on user preference.

What capacity coupler should I buy for my trailer?

You will need to find the gross trailer weight rating (GTWR) of your trailer. If the GTWR is not marked on the trailer, you should contact the trailer manufacturer. The capacity rating of the coupler must exceed the GTWR of the trailer.

What is a fold-away hinge kit?

These hinge kits are designed to be used with straight tongue couplers on boat trailers. They fit on a trailer tongue or tubing that is either 3”x3” or 3”x4”. They bolt on to the tube and can be folded away by pulling the clip then removing the pin. They provide the advantage of saving space by folding the tongue away for storage in a convenient place of your choice.

I recently had a small collision that damaged my coupler. Can I repair my coupler or should I replace it?

Various replacement parts are available for many couplers. Your choice of repair or replace will depend on which coupler you have and what specific part was damaged. Another consideration may relate to whether your coupler was a bolt-on or weld-on style coupler.

My straight tongue coupler is loose when it’s latched to my hitch ball. I already tightened the lock nut underneath the clamp mechanism, but that didn’t fix it. What should I do?

If you already tightened the lock nut and that didn’t resolve the loose fit, then the coupler’s internal parts are likely worn and need replacement. There are latch repair kits available for most couplers.

How do I maintain my coupler?

The most important part of maintenance is to keep the ball pocket and mechanism clean. In addition, the following procedures should be performed at least annually:

Check welds and mounting bolt torque.

Grease the ball pocket. 

Oil the pivot points with SAE 30 motor oil.

Inspect any retaining pins and replace if damaged or missing.

What types of trailer jacks are available?


Side mount

Pipe mount


Drop leg



What are the primary criteria I should know before selecting a trailer jack?

Where is the location of the mount? It is important to take note of any clearance issues, especially making sure the jack handle doesn’t interfere with the frame of the trailer.

You must know the fully retracted dimension of the jack. This dimension is important to ensure adequate ground clearance.

You must know how much travel or distance if required from the jack. This will ensure you will have the correct jack necessary to raise the trailer tongue above your tow vehicle’s hitch ball.

It is also important to note that a drop leg may be used for additional travel, especially if your required jack travel is greater than 15”.

What is an A-frame jack?

An A-frame jack is a smaller jack that mounts into the body of an A-frame coupler. They are typically 2K and 5K capacity and most often found on light-duty trailers.

What is a side-mount jack?

A side-mount jack is designed to either bolt or weld to the side of the frame of a trailer. The pivoting design of this jack allows the jack to swing up and out of the way for towing and down for storing when taking your trailer off.  Manual crank jacks side mount jacks are available in both top wind or side wind styles.

What is a pipe-mount jack?

Pipe-mount jacks have a square or round tube that is welded to the trailer frame, providing a mount for the jack to pivot on. The weld-on mounting method gives you more options for where you can mount the jack.

What is a swivel jack?

Swivel jacks provide great convenience when towing by allowing the jack to swivel up and be stored next to the trailer frame. Swivel jacks are available in both clamp-on and weld-on styles. A pull pin holds the jack in position where you can simply pull the pin to rotate the jack to change the position from vertical (down) to horizontal (up) when towing.

What is a drop leg jack?

The primary feature of a drop leg jack is that it provides fast leveling and an increased lift distance. 

Drop leg jacks are typically welded on to the front of a trailer. The drop leg action is created by pulling a pin on the leg to lower both the inner leg and the foot to the ground. 

This is accomplished by lining up the holes on the inner leg and outer leg and then reinserting the pin to lock the inner leg in the lower position. You then crank the jack to extend and raise the trailer. 

Because the inner leg and foot are close to the ground, you do not have to crank the jack as much to raise the trailer.

What is a stabilizing jack?

A stabilizing jack is most often a jack that bolts onto the trailer frame. A stabilizing jack typically folds up for storage and pulls down for use. These jacks are best suited for small utility trailer and pop-up campers.

What is a scissor jack?

A scissor jack is a type of stabilizing jack. A scissor jack typically bolts on or is welded to the trailer frame.  Scissor jacks are typically located at the corners of the trailer and operate by a screw gear (also called a worm gear) and handle. 

Scissor jacks are usually used in pairs and their primary function is to stabilize and level bigger campers.

What is the difference between a top wind and side wind jack?

A top wind jack has a handle that directly drives the jack screw. The rotation of the handle is horizontal.  A side wind jack has bevel gears that allow the rotation of the handle to be vertical. 

The main reason for using a side wind jack is for ease of cranking and for applications where a top wind handle would interfere with some part of the trailer structure.

What weight capacity of trailer jack is required for my trailer?

The rating of your jack must exceed the tongue weight of the trailer.

Can a manually operated trailer jack be driven by a power drill?

No. The internal components of a trailer jack are not made to work at the speed of a power drill.

Do I need a bottom support plate for my A-frame trailer jack?

Yes, a bottom support plate should be used to provide additional foundation structure for an A-frame jack. The A-frame plate is bolted or welded at the top of the trailer frame or A-frame coupler. The bottom support plate is welded to the underside of the trailer frame.

How do I maintain my trailer jack? How often is maintenance required?

There are a number of maintenance procedures that should be performed on an annual basis. 

For side-wind models, the internal gearing and bushings of the jack must be kept lubricated. To accomplish, apply a small amount of automotive grease to the internal gearing by removing the jack cover. You may also use a needle-nose applicator or standard grease gun on the lubrication point found on the side of the jack near the crank. 

To effectively lubricate, rotate the jack handle to distribute the grease evenly. Lightweight oil must be applied to the handle unit at both sides of the tube for side-wind models. If equipped, the axle bolt and nut assembly of the caster wheel must also be lubricated with the same lightweight oil.  

For top-wind models, apply lightweight oil to the screw stem. If your trailer jack is being used in a marine environment, flush the jack assembly and bushings with fresh water, and then apply fresh lubricant.

What are the benefits of a two-speed jack?

The benefit of a two-speed jack is the ease of handle effort required to lift the weight of the trailer.  When using the low gear, the handle effort will be lower but the speed with be slower. When used in high gear, the effort will be higher but the speed will be faster.