Fixing my brakes

I’m going to be getting my brakes fixed, and I was wondering what the vacuum plate is.

Do you mean “Backing Plate” in drum brakes?

That might be what it is. I filed a complaint with my state’s highway patrol because I didn’t get a proper safety inspection and on of the brake pads in the front actually came off the truck and they said something went through some kind of plate and that’s why I was leaking break fluid.