There are a couple of pieces of information that we need for your wash, and writing it with a peel-off marker lets everyone know how to handle your car. There is a 2 digit time stamp, a 3 digit wash code (that tells the tunnel which cleaning products go on your car), and a package code for the finishers to know how to treat your car. We will sometimes ask for your name and phone number if you are dropping off the vehicle and this will go on the car as well.