...
For example, https://uwarg-docs.atlassian.net/wiki/spaces/EL/pages/2694545459/LED+Board+Rev+3?search_id=824a823d-a091-44cd-a839-e67436297d92&additional_analytics=queryHash---e0fa16d9bc21f8c98c92d9fbd02b64297e9353182612e9bd2a87080f9ae2fbc1 uses M4 mounting holes and is intended to share bolts with a mechanical system.
Sizes
M3
3.40 mm hole diameter
0.10 mm hole diameter tolerance
6.00 mm annular ring diameter
Advised on any PCBA exceeding a board area of 900 mm^2 (this is most boards)
M2.5
Not recommended
M2
2.40 mm hole diameter
0.10 mm hole diameter tolerance
4.20 mm annular ring diameter
No Mounting Holes
Do this for any smaller boards because running holes smaller than M2 is not really practical as per past conversation .
Used on any PCBA with area less than 750mm^2
Mounting will be done with double sided sticky tape or Velcro and the board should be designed to facilitate this.
...