Acer Altos R920 Series User Manual page 175

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 154 for more information.
(2) Align and insert the mounting rail into the rack posts'
mounting holes (A).
(3) Make certain the proper mounting holes on the rack post are
selected.
(4) Use two metal screws to secure the front and rear mounting
rail to the rack (B).
(5) Do the same thing to the other mounting rail.
157