The 90 or mills double had slow and speed thread bolt .
Mills also had Burton spanner made (7inch) long handle made for the speed thread to stop or prevent the scaffolder from over tightening the fitting at the time
But it could have caused a weak link in the industry and so you have the myth of fittings not tightthen up when the next squad came to dismantle the job,,
Work onshore and offshore for them great fitting
it was always drilled in to us at the time use them in pairs as per company procedure
cant find any old paper work on this to say they were only load baring when used in pairs. ,same practice for the gravelock beam clamp