Like many magicians, I do a lot of pick a card tricks. A few times I've seen magicians do tricks where a chosen card is marked by tearing off a corner, to prove later on that it's the same card. I'm not sure, but I think I saw at a magic convention a gimmick that goes under the card that allows you to tear it exactly the same way each time. But I can't find it online. Does anyone know what this gimmick is called and where I could find it?

Gaetan Bloom's Intercessor is probably what you are looking for.

Thanks, that's exactly what I was looking for. The only problem is that I'd like to do it with jumbo cards. Anyone know if there's a jumbo size version?