I've just replaced all the side, front and back panes on a small greenhouse I installed in the early 1960's. Many of the panes were either cracked or broken - not too surprising after nearly sixty years. I was going to leave the roof panes, as I had got it into my head that they were all OK. But one wasn't, and I hadn't got enough new glass to replace it, and little hope of getting anything due to the lock-down. But one of the old and less-damaged Dutch Light side panes (730 x 1422 mm) was big enough to fit, if I could trim it down a bit to the right size.
I didn't attempt to cut and snap it in the usual glaziers' fashion, because I knew that old glass is almost impossible to break cleanly along the score-line, even if done by professionals, and anyway I'm hopeless at doing it even with new glass.
But I do have an old Plasplugs electric wet diamond-wheel tile cutter.
I knew I'd need to support the glass over it's entire area, both in front of the cutting wheel and beyond it, so that there was no stress on the glass as it was being cut. I set out a pattern of bricks covering about twice the area of the pane I was going to cut (about
1.5m x 1.5m), with the cutter roughly in the middle, marked up the pane and away I went, taking it slowly with only gentle push pressure. To my delight, and no little amount of surprise, it cut perfectly, a straight 730mm cut, which just goes to show that it is possible to cut old glass if you use the right tools in the right way.