Form a flattened C shape with the thumb and fingers. Open and close the fingers in front of the forehead to mimic the motion of grasping the rim of a baseball cap.
Form the hand into a fist with the thumb sticking up. Rub the thumb on the face from the cheek to the chin.
Beyer, Monica. 2006. Baby talk: A guide to using basic sign language to communicate with your baby. New York: Jeremy P. Tarcher/Penguin.