My campervan has a maintenance hatch with a door retainer. Because of a modification the existing retainer was too short.
My first design was just a simple extension(1, 40). Then I began thinking.
This extension could be hinged to let it stay on during the trip(8+20). As it needs much force to get the retainer fixed, a swiveling part would be nice (25+26). Another solution would be a spring type extension (13 small, 14 large). These parts were strong enough to hold the latch but would break if some force was exerted. So there is a part which gets a thread to accept the force (15).
The connector to the existing parts got a version which can be locked in place(30). And as I had so many different parts I made 4 more which have only grommets so that one can fix something with rope to them(41-44).
All hinged parts can be combined. A 3mm screw is used as axle.
In the end I used a simple screw on version with a hinge(23) and fixed part(24).
Supports and rafts can be useful for some parts.