Pretty simple. Just keeps you from changing any commands to one of your ships once you have marked it ready (single or double check). Disables most everything on the ship screen, turns off the attached hotkeys and ignores clicks on the map so you cannot accidentally change the waypoint. One downside is that you will also not be able to select other items via the map while a ship marked ready is active (you can once you close it), but that seemed tolerable. Unchecking a ship will allow you to edit it again.
Show Media Item - Utility Script: Lock ships when marked ready