This wiring method is the strut-type channel raceway. It's a metallic raceway that's supposed to be mounted to the surface or suspended from a structure. It may be called "strut channel" or just "strut" by field electricians [384.2]. But do not call it "unistrut" as Unistrut is a trade name.
There are eight permitted uses. They are: Where exposed, In dry locations, In locations subject to corrosive vapors (if protected by finishes suitable for the conditions), Where the voltage is 600V or less, As power poles, In hazardous locations (only Class I, Division 2) as permitted by 501.10(B)(3), As extensions of unbroken lengths through walls (or partitions or floors) where closure strips are removable from either side and the wall (or partition or floor) remains covered, and Indoors (if ferrous and protected only by enamel) [384.10].
Trick question! Article 384 lists only two. One is you can't use it where concealed. The other is you can't use it where subject to severe corrosive influences where subject to severe corrosive influences [384.12]. Now, for the trick part. The NEC lists other prohibited uses. Can you figure out what these are and where they are mentioned? Remember, all four Chapters of Chapters 1 - 4 apply generally to all installations. So, for example, you can't use this for something it's not listed for [110.3(B)]. You'll find gems like that in several places. Now, here's a brain teaser. Can you use it as an Equipment Grounding Conductor (EGC)? You'll find a list of wiring methods that can be used as EGC in 250.118. You may notice that strut isn't mentioned. But if you understand that strut is considered a surface raceway then you just have to make sure it's listed for grounding [250.118(14]..
- Secure the raceway with retention straps, if surface mount [384.30(A)]. For suspended raceway, use a method identified for the purpose (e.g., clamps) [384.30(B)]. In either case, the necessary parts are available from the manufacturer of the raceway. Ask your electrical distributor about what's available.
- You're not assembling this with couplings and connectors, so that's kind of a trick question. Just make sure you use the hardware recommended by the manufacturer. And don't forget the end caps!