"swivel top nuts for

[Crusty]

That's a good idea.

I often use coupling nuts to make various special fasteners and I've found that they can save me a lot of time. It's also relatively easy to make a split nut from one which can quickly engage/disengage from a threaded rod.

Here's a machinist jack that I made from one in less than an hour when I needed to support a part for milling.