No can opener?

So the drama today was that I had a tin of tuna with no ring pull, and the office has no can-opener. I had a salami sandwich instead. But I was surprised to learn that there is more than one way to open a can. More than 2 ways. All my life I had just assumed that the can and the can-opener were made for each other and there was no other way around it. Thankyou, friends.