what is the name for this kind of metal tube
 

What is this type of metal tubing called?

Its a C channel with inward fin (or flange) open seam.

If it's 1-5/8" x 1-5/8", Unistrut is one of the most common manufacturer's and generic name for it.

yep, unistrut.

That is used by plumbers---electricians and heating guys to mount equipment to building beams and walls----there are a lot of clips and fasteners made for that---comes in two common sizes and a couple of heavy duty odd ball sizes---

Some big box stores carry a limited stock of Uni-Strut

Thanks for the answers. I'd never seen it before. It looks versatile.

I just built a 20' span shelf overtop of my garage doors supported on 3 walls. I have the front face of the shelf supported by four 1/2" hanging threaded rod (strategically placed overtop of garage door opener rails and door rails) from these heavy duty struts lag bolted to my ceiling rafters in my finished garage. Works great!