Two down tacks (upside-down T shapes) stacked, a rare logic symbol.
U+2AE9SHORT UP TACK ABOVE SHORT DOWN TACKU+2AEBDOUBLE UP TACKU+2AE8SHORT UP TACK WITH UNDERBARU+2AECDOUBLE STROKE NOT SIGNU+2AE7SHORT DOWN TACK WITH OVERBARU+2AEDREVERSED DOUBLE STROKE NOT SIGNU+2AE6LONG DASH FROM LEFT MEMBER OF DOUBLE VERTICALU+2AEEDOES NOT DIVIDE WITH REVERSED NEGATION SLASHU+2AE5DOUBLE VERTICAL BAR DOUBLE LEFT TURNSTILEU+2AEFVERTICAL LINE WITH CIRCLE ABOVEU+2AE4VERTICAL BAR DOUBLE LEFT TURNSTILEU+2AF0VERTICAL LINE WITH CIRCLE BELOW256 characters in the Supplemental Mathematical Operators Unicode block, from number 235.
U+2AEADOUBLE DOWN TACKU+2AEBDOUBLE UP TACKU+2AECDOUBLE STROKE NOT SIGNU+2AEDREVERSED DOUBLE STROKE NOT SIGNU+2AEEDOES NOT DIVIDE WITH REVERSED NEGATION SLASHU+2AEFVERTICAL LINE WITH CIRCLE ABOVEU+2AF0VERTICAL LINE WITH CIRCLE BELOWU+2AF1DOWN TACK WITH CIRCLE BELOWU+2AF2PARALLEL WITH HORIZONTAL STROKEU+2AF3PARALLEL WITH TILDE OPERATORU+2AF4TRIPLE VERTICAL BAR BINARY RELATIONU+2AF5TRIPLE VERTICAL BAR WITH HORIZONTAL STROKEU+2AF6TRIPLE COLON OPERATORU+2AF7TRIPLE NESTED LESS-THANU+2AF8TRIPLE NESTED GREATER-THANU+2AF9DOUBLE-LINE SLANTED LESS-THAN OR EQUAL TOU+2AFADOUBLE-LINE SLANTED GREATER-THAN OR EQUAL TOU+2AFBTRIPLE SOLIDUS BINARY RELATIONU+2AFCLARGE TRIPLE VERTICAL BAR OPERATORU+2AFDDOUBLE SOLIDUS OPERATORU+2AFEWHITE VERTICAL BARU+2AFFN-ARY WHITE VERTICAL BAR