Sometimes, wearing a headlamp on your head can be a challenge, for example during rain or fog or when using a hat. An alternative is to wear the headlamp around your neck. But this can be uncomfortable and wobbly with most original holders.
This simple plate was designed to use the clamping part of the Skilhunt HB3 headlamp mount. Not only is it a great mount by itself, it is also easy to take apart and to design a compatible bracket for your headlamp yourself.
You can find the 3D model here:
https://www.printables.com/model/1483308-skilhunt-hb3-chestplate
(Before anyone gets worried: there's a weak link in the paracord.)
I used to do something similar when I was in maritime electronics servicing. It often involved dark and cramp spaces, and after bumping the headlamp in the bulkhead too many times I started wearing it around my neck instead. The light survived longer, and those few extra cm could be occupied by my head instead.