Re: Only cracking I have done is
I have done this, legitimately. I had a bike which had a locky-up thing with a combination lock (this was in the late 1970s before decent bike locks). I had cycled to the local town and locked the bike up before meeting some friends and spending the evening in the pub I think, having decided I could walk the bike home (no lights, not stupid enough to ride up the A5 in the dark, drunk, with no lights even as a teenager).
Problem: where I'd locked it up was dark, and it was midnight. So I spent what seemed like a long time (I was drunk, would have been less long if sober) solving the combination by feel: at any point the lock was hanging on one of the wheels, so when that wheel got into the right place the lock would move a bit, at which point you knew that digit was right. Iterate on the other wheels until it comes open. The 'drunk' problem was remembering which wheels you had solved, while not able to see the lock clearly.