How to sign the letter S in ASL

A closed fist with the thumb wrapped across the front of all curled fingers.

Easy to confuse. A rests the thumb upright against the side of the index finger. E curls the fingertips onto the thumb.

S is one of the six fisted letters - A, E, M, N, S, T - that differ only by where the thumb sits. You cannot check these on yourself, which is what the camera is for.