Actually just run through metal studs without the code required strap at each box.
The first place I saw it was a couple of years before it was permitted in the NEC. (It was all set to go into the code, but one of the metal conduit manufactures bought NFPA memberships for a number of their employees and the article was voted down on the floor of the NFPA meeting. It appeared in the code 3 years later, and was court a case that reached the US Supreme Court(Allied Tube and Conduit Corp. v. Indian Head) over the issue.)
It was at a prison and the door manufacture had installed a short length between the door position sensor and the lock assemble on the door buck. The ENT was bent in a 90 as tight as possible where it changed from the vertical run up the side to the horizontal run on the top. I looked at that and thought that there was no way we would get the wire around that, but the 3 stranded #18s pushed around it very easily.
(and people say that manufacturers would never attempt to have undue influence in the development of the NEC
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