As being a former fixture builder and now a cmm/quality leader, I can say that in the proper hands and used in the proper tooling situations, and height gage/indicator/gage block/gage pin set up will do a great job.

If you consider that, for instance, a checking fixture that has holes that are 90 to the base edges and you are only checking location from these bases, then a height gage/gage block/indicator/gage pin set up is perfectly acceptable. I will tell our builders that if they have a job that has holes 90 to the base edges and they can show me with a height gage/gage block/indicator/gage pin set up that they are in the correct location, I will gladly sign off. After they show me though, I personally go over the entire set up and make sure that it is correct.

I have personally done this several times and have had the fixtures sent out for third party inspection and have NEVER had a rejection, not even by the customer. I put on my header sheet that this was done in the lab and by me personally. Mind you, that I don't commonly practice this either, but only in the right situation with the right builder.

By the way....I also certify their tools before they show me.