For the record, to properly open a can with a knife:
1)set the can on a flat, solid surface.
2)position the knife tip directly over the center of the lid, holding the knife at the handle.
3)use the butt of your free hand, or a rock or pice of wood, and firmly tap the butt end of the knife, puncturing the can
4)saw through the can with the knife. Voila. Open can.
You can also repeat steps 2 and 3 all the way around the perimeter of the cancan, but it takes far more time.
Either way, there is little to no risk of cutting oneself.