he took his clipboard from the magnetized strip which held it to the center of the dash just above the driveshaft hump , flipped past the blank citation form all cops kept as a shield over the hot-sheet ( no need for the general public to be gawking at the license plate numbers the cops were particularly interested in while the cop to whom the sheet belonged was grabbing a hamburger or taking an express dump at a handy filling station ) , and ran his thumbnail down the fist .