This is a mount to get the Orange Pi 3 LTS and BTT Skr Pico v1.0 stacked one on top of another, mountable onto an aluminium extrusion.
It was made as part of the Deltabob project.
The standoffs should be printed on the side for strength, but will likely split if you directly screw into them. I recommend drilling and tapping out those holes while they're tightly clamped in a vise to prevent it tfrom splitting from the tapping stress.
The author marked this model as their own original creation.