There is such a thing as EIAA rack mount specifications that every manufacturer of audio and other equipment must follow so that products can be rack mounted in cabinet racks or road cases. These amplifiers cannot be mounted because the mounting holes are not in the right locations and the steel frame is not the right size. A very poor design which should be corrected immediately. You must resort to drilling and/or filing the mounting holes. There is no excuse for this. The one saving grace for these amps is that they are very cheap, and work well in a small church installation or other non-demanding low-budget application.