Acer Altos G530 - Manual (Page 172)

Appendix B: Acer Altos G530 rack installation guide 162
6 Install the M6 cage nuts (see page 157) into the rail.
(1) Insert the lower lip of the cage nut over the bottom of the
opening at the back of a rail.
(2) With your fingers, pinch the cage nut rack fastener and push
in until the top lip locks into position.
(3) Repeat this process to install the other cage nuts in their
appropriate locations.