Teach your baby the signs for the words in and out in baby sign language with the following descriptions and videos.
Hold the fingers of one hand outside the rounded fingers and thumb of the other hand. Put the fingers inside the other fingers.
Place the fingers of one hand inside the rounded fingers and thumb of the other hand. Pull the fingers out.
Beyer, Monica. 2006. Baby talk: A guide to using basic sign language to communicate with your baby. New York: Jeremy P. Tarcher/Penguin.