This looks very similar to a cabinet I recently aquired. It was an A/V cabinet that had PA equipment mounted in it. I measured and did my research and bought a set of square hole rails 48U that bolted right to the inside of the cabinet. I picked them up from a surplus location. I did have to do a little extra drilling, installing some nuts, bolts, and spacers to make it all the perfect width. I wanted the fully enclosed cabinet with glass all the way around it.