The letter D is signed by holding up your dominant hand, curving your middle, ring, and pinkie fingers together and touching them to your thumb, while only your index finger is standing upright.
This looks just like the small letter 'd'.
Teach your toddler the letter D sign when it is necessary to finger-spell some simple words - or the initials of objects, places, animals, or people's names. That way, your toddler slowly begins to associate the sign with the sound of the letter in a word or name.
This is a useful flash card taught best in conjunction with the other letters of the alphabet.