This is definitely not something I would try again without a drill press. I'm in an apartment with only access to a cordless drill, so of course the mounting holes for the vertical brackets didn't drill straight. It took quite a bit of work to get the bolts through the second piece of steel, and I severely damaged the threads on a bolt in the process. It was at this point that I realized the steel I had wouldn't work, and I had to dismantle it.

In an attempt to keep costs down, I had grabbed flat steel instead of angles. I suspected I'd have problems with the flats being too flimsy, but for half the cost of the angles, I thought I'd give it a shot. It was too flimsy.

I was excited to see that the angle steel alternated slots and round holes, instead of just a row of round holes like the flat steel. Surely this would solve my problem with the not-quite-straight bolt holes through the top/bottom horizontal bars ... or not. The slotted holes in the angle were 1/16" smaller than the round holes; the bolts didn't fit. Dremel to the rescue! Very few problems getting the bolts through the newly-expanded holes.

Almost starting to look like a press, now.