In the above photograph you see one unit installed in a rackmount cabinet at the bottom of the rack. APC supply very substantial rails with the unit but you have to use their supplied screws because standard rackmount screws are not compatible. No cage nuts are required for the installation. You can see that the APC rails will extend to fit cabinets with 1m depth. The cabinet above is set at 75cm depth of rails. You can see that the rails will reduce to a point just after the unit depth. The supplied screws required for the installation of a 2U unit are 2 for each side at the front and 3 for each side at the back. The rails are not true sliding rails. The unit is not fixed to the rails it only lies on top of pieces that support the unit from underneath.