Here’s my version of mikeho’s clamps posted earlier. While they are not unlike Rockler’s I think they are beefier, the nut is up on top, and I can make 3x as many for the price of the others. FWIW I used 3/8” x 5” U bolts (but the square ones whatever they are called), 1/4” pipe, and 1” x 3/16” flat stock. I’ve been needing these for a while and these work great!
-- Ray - Spokane, WA - “Most people don’t recognize opportunity because it’s usually disguised as hard work.” - Unknown