Place the two boards parallel to each other against the inside side supports on one side of the trailer. One 2-by-3-inch end of each board should be flat against the floor of the trailer and one 3-by-48-inch side of each board should be flush against the inside side supports of the trailer. Space the boards approximately 30 inches apart or the length of the trimmer shaft apart based on the size of your trimmers.
Slide one "U" bolt over each board approximately 12 inches from each end. The "U" bolt should extend past the side support of the trailer.
Slip a washer and nuts over the bolt from the outside of the trailer's sides. Tighten the nuts onto the "U" bolts with a wrench. This will secure the boards to the side supports of the trailer.
Drill a 1-inch deep pilot hole in the center of the 3-inch width of each board at 18, 30 and 42 inches up from the bottom of the trailer using a drill and pilot hole bit. The holes should be on the inside of the trailer.
Thread one hook into each hole on each board until the threads are all screwed into the wood boards. The hooks should be facing upright so that they will support the trimmers.