Some of the larger Swiss Army knives from Victorinox include
a small chisel on the back side, usually next to the corkscrew.
The chisel is pretty small, but it is good enough for mortising a hinge
or door lockset, if you are doing a repair and completely forgot
your regular chisel. It will take two or three times longer to do the job
with that tiny little chisel, but that can still be tolerable if your toolbox is miles away!
Uses: For best results, keep the chisel blade extremely sharp, and push with it rather than trying to hammer it. Note that the placement of the chisel blade is sometimes not very convenient-- since it pops out in the middle of the knife, you may not be able to maneuver it into the position you need.