If you work often in your yard, then you've probably had the need for a trailer at one time or another. Trailers are great for transporting large amounts of material including soil, rocks and even plants. Some trailers can be towed on public roads while others are only suited for use in the yard. Whatever your specific needs, there is a way to build or modify a trailer to suit them.
One of the simplest trailer designs is the flatbed. This type of trailer consists of a flat surface made of metal or wood with two wheels and a latch for attaching it to a truck or tractor. Flat beds are useful for carrying oddly sized loads but they lack sides and give little protection against the environment. You'll need to use straps to secure your load on a flat bed. But if you need to move trees, large rocks or other unusually shaped objects, this simple design might be your best bet.
Box trailers have some of the advantages of flatbeds. The added sides make them useful for carrying gravel, dirt, mulch or other loose items. You can design a box trailer that will pivot on its axle to dump its load or include a tailgate so that you can open the rear of the trailer and shovel out the contents. Like flatbeds, box trailers have an open top so they can accommodate large or unwieldy objects. In many states, box trailers with protective fenders and working safety lights are permitted on public roads if they pass an inspection and are registered for use. You may also consider building a box trailer with removable sides so that it can also function as a flatbed.
Short of building your own trailer, you may choose to modify an existing trailer. Horse trailers make a good starting point, offering a frame and wheels that are intended for use on roads and at high speeds. Stripping down a horse trailer by removing its body will leave you with a sizable flatbed trailer. Other candidates for modification should include smaller motorcycle trailers and simple metal carts, which may only need a new plywood base to be turned into a useful tool.
If your construction skills are a bit more advanced, consider making your own custom trailer without sticking to an existing plan or style. Usually, this will involve buying at least some prefabricated parts, including the tongue and latch to attach your trailer to a vehicle for towing and the wheels. Weld a custom frame or construct a trailer from wood that is the appropriate size for the type of work you do. You can add additional sets of wheels for a trailer that is more stable and can carry extra weight.