Step 3: Pipe Flange

Picture of Pipe Flange
The pipe flange is bolted through the ply-wood and 4"x2". Keep in mind the size of the flanges when you do your measuring to insure that you base (and other shelvs) are the size you want, because of the way I put the flanges I lost a bit of space on the bottom shelf and their positioning affects the size you can make the top and middle shelves.

since I used pre-cut ply-wood it was square enough if you cut your own make sure the wood is square and that the flanges end up square too.