I have used two pieces of 1/8"x 3/4" angle iron nested together, which seems stiff enough - not pictured, I add a support in the middle as well. Clamping the iron to upright brackets is to keep the iron aligned to the hammers - there is also support by wooden blocks beyond the range of that photo. To install, lay the iron at bench level, raise the hammers with the rail, get the iron aligned under the hammers at each end, then raise each end in turn. For the grand, raise all hammers, set the iron on supports, and align to end hammers, then drop all hammers onto the iron.