Epiroc employee was welding a square stock steel brace in place to support one side of 81 Drill A-frame for shipping. The other brace was leaning against the A-frame to be welded next. The brace fell and hit the Epiroc technician on the back while they were welding the first brace. The square stock measurements are 3""X1/4""X8'. They received a Transverse Process Fracture.