Dell OptiPlex GX1p User Manual page 70

Expansion-Card Cage Removal (Midsize Chassis): Dell™ OptiPlex™ GX1p
To remove an expansion-card cage, follow these steps:
1. Rotate the lever toward the back of the computer until it stops in the upright position.
2. Lift the expansion-card cage up and away from the computer.
To replace an expansion-card cage, keep it flush against the chassis to ensure that the lever engages the notch in the chassis when the lever is depressed.