Chevrolet Repair: Brake combination valve, push button, brakes

Question
I have a 72 El camino on the combination valve there is a push button. What is this for?  Do i need to depress this while i bleed the brakes?


Answer
The button is to reset the red brake light if there is a fluid difference in the front to the rear.  You should push it in once and then it wont have to be pressed again while you bleed the brakes.  After done bleeding if it is out again press it again.