A flatcar (US) (also flat car (US) or flat wagon (UIC)) is a piece of railroad (US) or railway (non-US) rolling stock that consists of an open, flat deck mounted on a pair of trucks (US) or bogies (UK), one at each end containing four or six wheels. Occasionally, flat cars designed to carry extra heavy or extra large loads are mounted on a pair (or rarely, more) of bogeys under each end . The deck of the car can be wood or steel, and the sides of the deck can include pockets for stakes or tie-down points to secure loads. Flatcars designed for carrying machinery have sliding chain assemblies recessed in the deck.