[tacticalogic]

If I knew I was going to have to give a thumbprint, I think I'd get a tube of superglue and trace the letters F. O. backwards across my thumbprint in advance.

[Johnny Gage]

Not a bad idea. how would they know. The one time I've seen thumbprints being asked for (at my bank), they've used some type of "clear ink" that has to be treated with something before it's visible. (It says this right on the card)
What if you "glued over" your thumbprint with a thin layer of glue??? How would they know?