line lock orientation

hey friends, while this snowball is rolling along, i figured i now is as good a time as any to install a line lock

my plan is to install it on the rear brakes, locking brake fluid OUT of the system, rather then in, so i can control roll out after the burn out (and maintain proper brake lights)

now, if i do it like that, will i need to install it backwards?
(the instructions say one side should point towards the master cylinder, the other towards the brakes)

i guess my main concern is, is this valve CLOSED when closed, or does it act as a one way valve, when it is closed?

does that make sense?


and would anyone know off hand what size thread is on the rear distribution block on a 8 3/4 with 10 inch brakes?