The call for chocks and chains can elevate the heartrate of any US Navy "airdale", or flight detachment member.

When a helicopter lands, it uses either the RAST system or it "freedecks" (lands with no RAST trap deployed). When the helo is down, the LSO announces that the wheels should have a set of chocks installed to prevent rolling, and the lower mounting point area on the main landing gear should have two chain sets installed and tightened to keep the helo from tipping or rolling over the chocks.

Oh, did I mention that the helo is still turning its rotors at full rate and there's only eight feet between you and the safety nets (or the ocean)?

When a helo is turning, it is creating a large amount of vibrations. These vibrations can be dampened by the main landing gear struts. One should NEVER install chains to the tie-down points that are hard-mounted to the helo airframe. Aircraft have hit a sympathetic vibration point and have literally shaken themselves to pieces in less than a minute. That's why chains are only used on landing gear.

When the helo is set to take off, the call comes again, and the two teams (one on each side) pull the chains and the chocks, show them to the LSO, then bring them into the hangar. Sometimes, if both teams are made up of members of the air detachment, they will have races to see who can remove or apply chocks with no safety errors.