Horizontal rails?

[taggart]

So far nearly everything in this project and nearly all builds are using vertical posts. Things like shelves depend on gravity to hold their contents, etc.

Should it be a goal to be able to mount these racks with horizontal rails and vertical components? Or if not a goal, at least indicate which things won't work that way, and/or aim to produce designs that will.

Note: the eurorack and DIN standards mentioned in #32 #47 have horizontal rails and vertical components and that seems pretty nice. It would allow for more flexibility for where you could put miniracks.