lazermonkey,

Guilty! <img src="/images/graemlins/blush.gif" alt="" />

When I was in the army in the 1980s we got C-rations. They had food in cans. I had a small Buck 503 folding knife I kept in my pocket. I would start by stabbing the top of the can by the rim. Then I used a push-rock motion to open the can the rest of the way. It left sharp jagged edges. It was hell on the plastic spoons and forks they gave us. Other than that it worked OK. I don't know that it hurt my knife any. Needed sharpening a little sooner.