I think the title is self explanatory. It has a number of uses. I know some ports have it (JDoom?). Aside from anything else, I'd like to give the player a little 4 unit boost to his height. That seems to be how much taller the monster sprites seem to get by being shifted up to stop their feet dragging through the floor. It's only fair that the Doomguy gets a little taller too.
Crouching compatible of course.
