Whack your forehead with the back of a "V" hand.
Whack your forehead with the "palm side" of a handshape that is a cross
between an "A" hand and an "S" hand.
(By that I mean the fingers are tucked in as in an "S" handshape, but the
thumb is tucked to the side of the hand as in an "A" handshape instead of
wrapping around the front of the hand.)
American Sign Language University ™ ASL resources by Lifeprint.com © Dr. William Vicars