Lenovo ThinkSystem SR645 V3 User Manual page 56

A video of this procedure is available at YouTube:
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Procedure
Step 1. Loosen the two thumbscrews located on the front of the server to disengage it from the rack.
Rack front
Figure 17. Disengaging server from the rack
Latches
1
Thumbscrew
2
Step 2. Hold the mounting ears on the front of the server; then, slide the server all the way out until it stops.
ThinkSystem SR645 V3 User Guide
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https://www.youtube.com/playlist?list=PLYV5R7hVcs-