This is part of a system of prints that turns an OpenBeam into an optical rail. An optical rail is a long, straight, sturdy rail onto which optical components such as light sources and lenses can be bolted down and easily shifted along the length of the rail.

Commercial optical rail sells for $380/m ($115/ft). Open beam only costs $12/m for the fancy black anodized stuff. You get the idea.

This component is part of the Open-source optics project, whose goal is to radically reduce the cost of scientific optical hardware: by the Michigan Tech's Open Sustainability Technology Research Group.

For similar see the Open-Source Lab How to Build Your Own Hardware and Reduce Research Costs