Jeeeees... it's a cross between a wotsit and a thinggy...... Those are two other REME Armourers technical terms indicating that he hasn't got a clue. At this stage, the querie would be passed to the senior Armourer Sergeant who would come back with an answer, tell me, then I'd get the credit!!!!!

But seriously, after the first recoil from a No4, the back end would split like there's no tomorrow!