Our square hole rack rail is used in the assembly of our QF series of steel racks.  Typically, as with our Pre-Pack Rack Kits with 3/8" Square mounting holes, these racks are assembly with the 3/8" square holes facing forward and rearward for attachment of quick release component glide and attachment systems available from numerous manufacturers of computer servers and related devices.  Remember, though, that due to the unique design concept of these racks, you can choose from our list of 43 distinct rail lengths (1U - 43U) of any combination of square hole rail sets (opposite rail leg is 10-32 tapped) or double 10-32 tapped rail sets to achieve a multitude of different hole patterns and component mounting possibilities.