The easiest way to sign don’t know is to shrug your shoulders. Alternatively, you can point to your forehead with your dominant hand with fingers together and move your hand away from you, while slightly shaking your head to show negation.
We use don’t know in context when our babies are learning to provide simple information about situations. For example, you could ask if they know the location of an object and have them assert or deny their knowledge using the sign for yes or the sign for don’t know.
Use the don’t know flash card when showing your toddler lack of familiarity with something. For example, you don’t know where their pinkie is.