Ahh. Well, its kinda the same thing, just for pipes though.
I've tried to do that dimension thing too but I never got it to work. I could never get anything to go horizontal. It always ended up being sloped like the pipe, or worse. I tried starting two lines from the ends of a flow direction arrow set at the center of a pipe and then ending them at the pipe 'dimension'. I thought they would go from the ends to a point below the ends (same elevation using a 'fixed' dimension) ... no go, they ended at a common point below the mid-point of the pipe. Doh!. I gave up after that.