[SCRIPT] Custom hatch falls through the floor

[Daemian]

Yes, set its parent/child. Parent for the static body, child for the door. So, two bodies.
Gravity on the door should be on, mass about 5 or 10, and collision with player/stuff on.
If the door goes mad in-game, make its body a little smaller than the model, so it doesn't collide with any border or anything nearby.
Check the attachments as well, the door model should be attached only to the body you made for it.
For your hatch I think you're gonna need to enable that option named Sticky Minimum on the hinge so the door stays in place until the player comes and moves it.