To test for a twisted body we had a BODY PLATE. This was a 3/8 or 1/2" thick steel machined flat plate that had cut-outs of different sizes to cater for the front trigger guard screw and the block for the drawers/sear axis block. This was configured for the No1 rifle on one side and the No4 and 5 rifle on the other side. The plate could be held/clamped in the leather vice jaws. The body is placed on the plate and it should sit flat and not rock left/right or bow front to rear. Nothing too complicated. But the bodies are real basxxxxx to UN twist. We wouldn't bother even trying...... as when they came in to us it was usually for some other reason. I do recall that when a rifle was sentenced ZF for a twisted body it had to go back with the G-1043 paperwork marked in a certain way (forget but will check.......) to the effect that the condemnation was total