The rack should be attached to the wiring closet floor with 3/8-inch (9.5 mm) lag screws or equivalent hardware.
The floor under the rack should be level within 3/16-inch (5 mm). Use a floor-leveling cement compound if necessary or bolt the racks to the floor as shown.
Brace open equipment racks if the channel thickness is less than 1/4 inch (6.4 mm).