Dell EMC PowerSwitch Z9432F-ON Installation Manual page 18

For EIA 7.1 mm (.279 in) round hold racks, press the latch to change from square pegs to round pegs.
For a threaded mounting hole, change the die-cast parts on the outer rail to the fitting plates shipped with the rails. Change
the die-cast parts on both the front and rear side of the outer rail.
5. Attach the outer rail to the back of the four-post rack.
Align the outer rail pegs to the back of the four-post rack and push towards the back to lock the outer rail to the rear post.
The rail clicks into place.
Threaded mounting rack
18 Z9432F-ON switch installation