Most of the bolt trailers are bolted together. Hence, it is always recommended to start your corrosion check by inspecting all the bolts including u-bolts, nuts and the washers. U-bolts are the most important hardware to check as they fasten the leaf springs and axle together. If these corrode, the axle will separate from the trailer which is the most common issues that people face. If on inspection, you find a bit of rust on the surface, it won't be a problem but this corrosion can eventually degrade the u-bolts to the extent that they can no longer handle the pressure imposed at this point. Apart from u-bolts, the other boat trailer parts that need to be examined are leaf spring centre pins, spring shackles and shackle bolts, spring hangers and equalizer bars, fender hardware and brackets, bunk or roller bracket to frame hardware, wheel lug nuts or bolts and studs and cross-member to frame hardware for boat trailers for sale.