The next task is to open up the large hole at the top to allow the power booster to fit. We used an air-powered grinder with a small grinding bit attached. The directions and a supplied gasket or template illustrate how much material needs to be removed. The directions also say to enlarge the two smaller holes on either side of the large hole to allow the brake booster to fit. By test fitting the booster/master, we discovered that we didn't have to do this with our car.