How to find tdc

I "learned" these when I was in the Navy at Miramar, part time job at the auto hobby shop. The "purpose" of my job was to operate the (Allen) tune up scope and assist guys with tune ups. That job turned out to be a lot more. A friend of mine came up with this, obviously LONG before the internet. Some Fords we got in obviously had either a cam timing issue or slipped balancer. It turned out to be a little of both. he came in one day and described this thing called a "piston stop" and it wasn't long before we were cutting spark plugs open and tapping the small end for a bolt. We made several while I was there