Abstract: The invention is a cart assembly having an upper and a lower deck whose body may be assembled in a single procedure using only one hand and whose body including the wheels can collapse to fit behind the driver's seat of a standard cab version of any size pickup truck. Specifically, a plurality of spacing members rotatably connected between the upper deck and lower deck rotate to alternately collapse and expand the cart. The cart is held in a fixed position by a brace member disposed diagonally between the upper deck and lower deck in the expanded position of the cart, and which is disposed in parallel to the upper deck and lower deck when the cart assumes its collapsed position. The brace member fixes the relative positions of the upper deck and the lower deck as the brace member has a length (and thus radius of curvature) unequal to the length (and thus radius of curvature) of the spacing member.