This 3 port vacuum valve controls the wiper door down movement by blocking vacuum (to relay valve) when right wiper arm is out of park position.
Main vacuum attaches to white port, which should be completely blocked until plunger is depressed, when depressed the main vacuum flows through to the red port (red port is a bleed until the plunger is depressed)
Products may be labeled as fitting either the left or right side. The left or right side can be determined by your position while sitting in the car facing forward. Your left would be the left side and your right would be the right side.