Cut the drawbar components as per the plan below. Drill the cable routing hole and shackle hole as shown. This can be done later but if you have access to a drill press, now is the ideal time to prep the drawbar section.
Note - The left hand drawbar section is shown, holes are not necesary in the right hand section unless an additional safety chain is required.
For Australian Trailer Builders - The shackle hole and shackle plate are not required as your safety chain regulations require the chain to be permanently fixed (welded) to the drawbar. See here for more details.