L-Acoustics X12 Owner's Manual page 53

Rigging procedures
6. Lift the enclosure by the knobs and place it inside the U-bracket.
Adjust the knobs on both sides so that the safety washer is between the hook and the enclosure.
7. Push until the knobs are locked inside the spring-lock safety mechanism.
X12 owner's manual (EN) version 1.0 53