Acer Altos G540 M2 - Manual (Page 172)

Appendix B: Rack mount configuration 164
(3) Do the same thing to the other mounting rail.
Caution! To avoid personal injury, care should be taken when
pressing the inner rail release latches and sliding the component
into the rack.
2 Attach the inner rails to both sides of the server.
Please use screws that came with the rack-mount kit when
attaching the inner rails to both sides of the server. If your system
already has screws attached, please remove them.
Note: Using screws other than those supplied in this rack-mount
kit to attach the rails will void the warranty, Acer cannot be held
responsible for any damage for incorrect installation.
(1) Align the screw holes of the inner rail to the server screws.
(2) Slide the rails to the left until the rails lock into place with an
audible click.
(3) Align the handle on both sides of the server.
(4) Screw in place the handle on both sides of the server.