I'm still getting counselling from the cone / triangle thing that had to be hand filed to fit a 1/2 thick plate with a square , triangle and round hole. We were allowed about 10 thou, if it was wrong it went in the bin and you started again. It took nearly a week to make one. One of the worst parts was filling the flat on the bar but leaving the base round, one slip and it was in the bin. I still have it in a box, in a box, in another box with 3 locks, just to be sure it never gets out.