Quarter turn electronic equipment box battery door latch / clasp

Having recently completed building an ESR Meter (capacitor tester) from a kit (Altronics #K2574 https://www.altronics.com.au/p/k2574-esr-meter-kit) I wanted the batteries to be accessible from underneath, without having to unscrew the top panel to replace them each time.
To that end, I mounted the AAA battery holders on a plate, marked out and cut a door panel in the supplied plastic zippy box, and designed this old-style latch to keep the door closed.

It operates in a similar manner to the type of latches that use a coin to open, although given the smaller size this one just requires a flat-bladed screwdriver or even your thumbnail to operate. A quarter turn retracts the arm into the retainer and the door may be opened.

The customiser is set for a drill diameter of 10mm and matching box thickness of about 1.5mm but feel free to alter those if you wish.

Supplied are the STLs for 10mm dia at 1.5mm thick one I used, and also a 1/2" dia at 1/16" thick version if you have imperial drillbits.

Print at 100% (solid) infill only. I used yellow ABS, I think PETG would also be fine. I would not recommend PLA as it is more brittle.

See fitting instructions below. This is easily accomplished with CA/Superglue, but there are fixing holes if you wish to use small self-tapping screws.

The three parts are printed on a sprue, so you can run off a number of these and keep them in your electronics parts box for future use.

FITTING INSTRUCTIONS

1. Remove arm from clip/retainer by cutting single sprue with an X-acto blade. Remove flash from detent indents and underneath.
   NOTE Do not cut the two sprues linking the retainer to the clip yet!
2. Position the retainer/clip inside the box door so the door gap coincides with the gap between these parts.
3. Use a scriber or sharp point through the circular boss centre to mark the hole to be drilled.
4. Remove retainer/clip and centrepunch the mark, pilot drill and drill to 10mm or your arm disc size.
5. Snap the arm onto the boss so it sticks out, invert and fit the arm disc through your drilled hole.
   Ensure the hole is sufficient to not bind when turning the arm. Use a sharp X-acto blade to de-burr and enlarge the hole if necessary.
6. Position the retainer/clip so the gap between them is straight across the door gap.
7. Apply a drop of CA/Superglue to the short sides of the retainer and clip respectively.
8. When set, cut the two sprues between the retainer and clip with an X-acto blade.
9. Use a flat screwdriver blade to turn the latch arm and check it clicks into the detent spring nub at the three positions.