Perhaps another illustration is in order?
Hmmm..... we never had any of the tiny 4" ones with the screw tabs at work, ... the greenies came in a jug-o-ties from H/F, I bought long ago.
As for the hole -a-bob thing, that's for mounting the harness to a panelboard with a screw, we used the ones like in the picture by the thousands where I used to work.
Used to really pizzz me of when I designed a 36" x 48" panelboard that mounted a bazillion components, pwb's, transormers, relays, and stuff, and accounted for every possible mounting screw for all of them, including fastening the harnesses, with pre installed captive fasteners, (nuts, studs, standoffs etc) and the goobers assembling them would devaite from my assembly drawings and use peel and stick tie wrap mounts all over.... arggggg......
So much for the 800+ holes and pressed in fasteners...