Title 70 of the Pennsylvania Code
Wood used for fuel shall be sold by the cord of 128 cubic feet (4 feet by 4 feet by 8 feet) or fraction thereof and shall be accompanied by a statement or invoice certifying the amount sold and presented to the buyer or his designee at the time of delivery or billing.
Section 2.11 of the Weights & Measures Act of 1965
Cord: When used in connection with wood intended for fuel purposes, the amount of wood that is contained in a space of 128 cubic feet (4 feet by 4 feet by 8 feet) when the wood is racked and well stowed.
Firewood may not be advertised or sold by the truck load, the pile, the piece or any other method other than by the cord or fraction thereof. There is no such thing as a face cord. An invoice must be given at the time of sale.