Inliners International Forums General Discussion Hi Performance Installing a brake booster on a non brake booster system

This has got to be a stupid question. I have done it before but dont own the tool. To check a vacuum advance or a brake booster I need a vacuum gage right? I have seen tools that you jam in the hose and check engine vacuum but what is the tool that is used to check these? Does anyone have a picture or know of one being sold on e-bay...thanks