...and band type hose clamps, found in automobile supply stores and hardware stores (since they are also used for in-ground lawn sprinkler connections). Because of the hex-head screws they can be made incredibly tight. (It would be easy to break a plastic "milk crate", so watch it.) They are stainless steel, so won't rust. If you need some "grip" so the clamp doesn't slide, or something to fill the slack, cut some rubber from a tire tube and put it under the the clamp.



By the way, those plastic ties broke the first time my bike fell. (Actually I put them as additions as a sort of field test. I didn't think they were as fragile as they turned out to be though.) Maybe some huge ties like they use on trailers would be reliable, I don't know.

The band clamps, being slightly stiff, relax over the months as they gradually adapt to the shape of what they are wrapped around, becoming loose, so it is good to put something with a little give (such as plastic) under them. The plastic expands a little as the pressure eases, keeping the bands tighter longer. Although rubber is good for grip, it squishes a little too easy to get things really tight (if you need it that tight).

Other clamps I know about are in the electrical department. They have some C-type wrap-around clamps with an integral plastic/rubber insert.

There are iron pipe-hanger brackets in the plumbing department. These are the kind that are about 1/2 wide, not the kind that look like wire clothes-hangers. They are used to anchor pipes to joists in basements. They have holes to be nailed to the joists, and the holes can be used for your screws. They come in all sorts of sizes and are dirt cheap. You would have to bend them to wrap all the way around a frame or rack. They are pretty stiff (which is good) but not so stiff you can't bend them with pliers.