Closeup of casters on my recent build. David Schlitter asked about these in the video. After buying the first pair I liked them so much that I now use them everywhere in my shop. They are inexpensive, low profile, smooth rolling, with dual action brakes to lockout both the roll and swivel. The bolt pattern matches the straps perfectly. The plywood is to keep them from spinning around the pipe, it’s not load bearing other than the flat pressure directly at the mount. Handy for when you want a caster that is not directly at a vertical pipe end.

https://www.amazon.com/dp/B07CMTDPBT/ref=cm_sw_r_cp_api_glt_fabc_X0S2NRCH1M5DVSEW3X6A?_encoding=UTF8&psc=1