Dell Precision T7600 (Mid 2012) - Manual (Page 46)

Power Supply Unit (PSU) Lock
The PSU lock prevents the removal of the PSU from the chassis.
NOTE: To lock or unlock the PSU, always ensure that the cover of the chassis is removed. For information on
removing the left cover, see Removing the left cover.
To secure the PSU, remove the screw from the unlock screw location and tighten the screw to the lock location.
Similarly, to unlock the PSU, remove the screw from the lock screw location and tighten the screw to the unlock screw
location.
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