The sap gauge
This is the gauge that shows how much sap is going into the tank. This gauge is attached to the tank outside, once the sap in this gauge drops to a certain point, then more sap is let into the tank. This gauge is supposed to be always at least 1.5 or a little higher / lower on the gauge. If the sap is lower than 1.5, then it can cause the sap in the tank to boil too much and cause the sugar and other ingredients in the sap to burn. This is what is never to happen.