Like a pole barn my shop has wooden wall purlins spaced 3'6" on center. I lucked into some old retail shelving from a drug store. I used a metal butting blade in an old Sears $99 table saw to rip the stantions in two. If I was doing the job today I would most likely use a plasma cutter. I welded tabs to the split stantions 3'6" on center and screwed them to the purlins. Lots of good adjustable shelving for cheap. You can find this kind of shelving if you know where to look. Ask the manager of your local grocery if they have any excess or if if he knows where you can get some. It also comes up for sale at going out of business auctions. I have since made additional shelving for a friends shop and located more shelving for use in my shop.