Toolless rail mounting for a computer system rack

A rack for supporting electronic devices and modules with adjustable rails. The rack has a vertical wall with a set of holes at various elevations, each set of holes including at least a proximal hole evenly spaced apart from a distal hole. A longitudinally-extending rail has a set of clips for selectively securing the rail to the vertical wall, wherein the set of clips includes at least a proximal clip selectively receivable in the proximal hole at a selected elevation for supporting a proximal end of the rail and a distal clip selectively receivable in the distal hole at the selected elevation for supporting a distal end of the rail. The system may include a second rail for securing to an opposing vertical wall of the rack to form a shelf or bay for an electronic device. Each rail may be latched in place and can be selectively installed and removed without use of tools.