Nissan Repair: brakes, swamp buggy, vacuum booster

Question
I'm building a swamp buggy bought a nissan brakebooster &master cyl. on the top of the booster is a small pipe  nothing hooked to it. what is it?

Answer
Glen,

There should be one line coming off the vacuum booster and it is to be connected to engine vacuum to run it.  Make sure you have a check valve for the booster.  If there is another line on the booster and it is smaller just plug it.  If your master sylinder has three connections two are for the front brakes and one is for the rear.