The way to use a straight as a weapon is to open the razor and hold the scales in your closed fist with the blade all the way open on the outside of your fist and, obviously, the edge pointing away from you. You can then make punching motions towards the face with a hooking motion. It leaves a nasty cut on the face and arms, if raised in defense. You're not going to kill the other guy, unless you're lucky and hit an artery in the neck, but it will keep an attacker away.