When I was a kid, there was a little sliding blade pen knife on the market called a Christy knife. Kind of a stamped out metal frame handle with a razor thin blade that slid up out of the handle. The blade locked in a couple of positions like half out, three quarters out, and in truth was a very handy little cutter. For the past month I've been using one again, and I'd forgotten how handy it was. I had been rooting around in some very old boxes up in the attic when I found the old one my dad had given me. The blade was worn down thinner than it had been when new, but a few strokes on a diamond rod and it was good to go. The Christy knife company had never been a big operation, and they went out of business when the owner, a mister Earl (?) Christy died. Now I understand his son had restarted the company, and I ordered a new replacement blade for 5 dollars. The new blade fit right into the old frame with a minutes work. Two screws and it was done. The Christy has gotten kind of expensive for what it is now, and the one hand knife is the norm these days. But way back in the 1930's and 40's, the Christy was the original one hand or easy opener. They were even used by air crews during WW2. I just may buy a new one just for the sake of nostalgia, not to mention the tool like aspect of the little knife. People who see it are captivated by it, even in this extreme political correct Washington D.C. area. It goes right under the radar, and the security people who do see it, think of it as just a little key chain knife/trinket. But the thin blade opens boxes, cuts string and rope, opens those blasted plastic blister packages that almost need explosives, and do snack duty in the kitchen slicing off a piece of cheddar for a cracker. Add in the fact that replacement blades can be had cheap, and the Christy knife is still a viable little pen knife for our times.