Acer Altos R720 Series User Manual page 173

3 Install the mounting rails to the rack posts.
(1) Determine the vertical position in the rack. Refer to "Vertical
mounting hole pattern" on page 160 for more information.
(2) Align and insert the mounting rails into the rack posts'
mounting holes (A).
(3) Make certain the proper mounting holes on rack post are
selected.
(4) Use two metal screws supplied with the kit to secure the front
and rear mounting rail to the rack (B).
(5) Do the same thing to the other mounting rail.
163