To sign leg, take your dominant hand's index finger and just point it up and down one leg, starting from the hip, down to the fore leg, and back up.
Teach your child the leg sign in context: when you are teaching the body parts to your toddler, or when you are instructing them to lift one leg at a time and put on their pants, and so on.
Teach your toddler this sign along with the other body parts when they are ready. It is good to complement the body parts flash cards with nursery rhymes, like "Head, Shoulders, Knees and Toes".
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