Quote:
On the top of the vacuum gauge there is a rubber with a small plastic like switch that can be set in open or close position...
This is a valve. When you take the gauge out of the box, hold it so the rubber is to the top and turn the valve open for a few seconds. This "zero's" the gauge to the elevation you are at. Close the valve and it's ready to go. 
1982 Pontiac Trans Am...K.I.T.T. in progress.
"It looks like Darth Vaders bathroom in here..."
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