Several factors will influence the steps that need to be taken to build DIY trailers, the most significant of which is the intended purpose for the unit or units. It is possible to build DIY trailers that are not for use on roads quickly, easily, and safely, but building one that is intended for use on roads can be trickier, more time-consuming, and ultimately more expensive. If the trailer is intended for road use, the first step in the building process should be what steps must be taken to make the unit street legal.
One way to ensure DIY trailers are street legal is to buy trailer kits. These kits will generally include all the necessary components to build the unit properly and within legal limits, but the builder will need to have some carpentry skills or knowledge of welding if the frame of the trailer will be metal. Smaller kits for DIY trailers are also available for units that will not be used on-road; these tend to be less expensive and less difficult to construct, but they will not include components commonly included with street legal units, such as tail lights, braking systems, and license plate holders. The axles and tires are likely to be less durable as well.
It is important for the builder to think not only about where the trailer will be used, but also what it will be intended to haul. Sometimes DIY trailers can be designed to accommodate a specific application, such as hauling a car or motorcycle. In other cases, trailers can be built in a more general way to accommodate various applications. The trailers may be enclosed or open-air; enclosed trailers are generally more difficult to build and more expensive since more materials will be necessary to complete the project.
One of the biggest challenges to building DIY trailers is building a unit that is straight. If the trailer is built crooked or otherwise improperly, the likelihood of the unit tipping over or breaking away from the towing vehicle is greatly increased. Damage to the trailer itself is also much more likely. To ensure the trailer or trailers are built squarely and straight, it is a good idea to build a jig out of metal or wood; when materials are being joined together, the jig can be used to ensure the angles are straight, thereby preventing the trailers from being built improperly.