Cut the angle iron into 12 pieces using a cut-off saw. Four of these pieces will be the vertical sides and they should be cut to between 1 and 1 ½ feet. The other eight should be divided into two sets of four: four for the length and four for the width of the trailer. Use only three pieces for the width if you want an open-back trailer.
Drill a hole at each end of the bar and drill two additional holes, one on each side of the "L" shape.
Measure the two long bottom pieces to locate the exact center. Drill holes in the center. Choose which side of the bar you want the hitch to be.
Drill two holes one-quarter of the way from the end of each bar. Attach the crossbar here. These are the pieces the tongue will attach to.
Choose one of the short pieces and drill a hole in the center. This piece will be for the end with the hitch.
Bolt the angled pieces together to form a cube frame.
Measure a flat iron bar to place across the bottom of the frame. Drill a hole in the center of the bar and bolt it to the cube frame.
Cut a metal bar long enough to span from the crossbar to the front end of the trailer. This bar should leave 1 to 1 ½ inches to spare. This bar is called the tongue.
Drill holes in the bar identical to the holes in the frame and attach the hitch at one end. Bolt the entire piece to the frame.
Read the manufacturer’s instructions for your axle kit to bolt the axle and wheels to the frame.
Saw a piece of plywood to fit in the bottom of the trailer.
Cut additional pieces of plywood to sit flat against the sides of the trailer frame.
Place the wood pieces in the trailer and screw in L brackets in the side and bottom pieces to keep them secure.