IBM 1U Installation And Maintenance Manual page 23

7. Loosen the front four slide-rail bracket screws, and then insert the
rail-alignment spacer into the middle holes in the slide rails. The rail-alignment
spacer must wrap around the rails to align them correctly. Tighten the front four
screws and remove the spacer.
Note: Do not tighten the four rear slide-rail bracket screws at this time.
Rail-alignment spacer
8. Extend the inner part of the outer rails and slide the ball-bearing assemblies
forward to the front of the outer rails. Carefully slide the console unit into the
ball-bearing assemblies in the rails.
Chapter 2. Installing the console unit in the rack cabinet
13