Better question. Hope this is easier to answer.

[khartline10]

What is the recoginized height per OSHA that a rack needs to have capacity lables applied? Then at that point is it no longer concidered a shelf?

 

[mcgyvr]

Where do you see any mention of capacity labels in OSHA?
I don't think height matters in the definition of rack versus shelf

I've always thought a
shelf was a flat closed surface for holding items...
and a rack is a system of uprights/horizontals that are used to secure objects on that do not necessarily have flat surfaces. (i.e. pegs sticking out or grills/mesh,etc..)