Yes, I used remnants of an old project (2" x 4" x 8' not pressure wood) they slip right into place. I needed to apply a bit of pressure to anchor in the side screws (not included). I gave them a polite hole to keep in place, I have cats … ha, ha, … so far so good …. I split two sets one rack 3' the other 5' two cuts in the remnant wood …. indoors?
I do not know anything about the garden club, these brackets should give you a good run for your money outdoors. I have mine indoors, split two sets with two pieces of wood 2" x 4" x 8' they work great! Pressure treated wood, probably last longer?
I would not recommend installing casters.
I think 8' long would be the max to use. The 2x4s are just an 1/8" off the ground so wouldn't expect a problem with the screws.
Not sure of gage, but it is adequate. Tubing is welded to brackets.
We did and never had a problem. Just don't put too long screws in. For our permanent storage, we used longer stainless screws to last in the weather with the treated 2 x 4s.
Made in China.
About 42" including the 2x4 support.
2 vertical supports, each one a U-shape so you don't need a 2x4 crosspiece on the end, Just 2 2x4's of the desired length