Used to be whatever was agreed between despatcher and flight deck
Stitched up now by acars, and it's parkbrake set and engines shutdown and sent to Ops electronically
Our company define it as chocks off to chocks on. ACARS times are triggered by parking brake being released and movement. Can be overridden if waiting 15 minutes for the ground handling agent to turn up and physically insert the chocks, as happened recently to us at home base
