Visor mount

Looking for a little help, my son did a 3D printed visor for my HDS-12 Carbon. It fits great but I’m not sure how to mount it. It has the holes in it but I’m wondering if anyone else has dealt with this. The holes it aligns with are not threaded, they look like they go all the way through to the back of the faceplate and they’re shaped like a kettlebell weight. Attachment 509276
Attachment 509277

Might post this on the fishing electronics section of this board. They are smarter than us MO guys. :cheers2