A slatwall extrusion and assembly for a wall of a building to support hangers and shelving and the items they carry. Each section of slatwall has a continuous linear rear wall that integrally joins number of spaced boards. Each board has front, rear, top and bottom walls that form a continuous loop around a hollow interior. Each board also has a downwardly extending double-walled lip. The lip is spaced from its adjacent lower board to form an L-shaped slot. The continuous rear wall is firmly secured to the studs or drywall of the wall by self tapping screws or an adhesive coating. The linear rear wall, hoop shaped boards, and double-walled lips combine to form a sturdy, lightweight and inexpensive slatwall extrusion. High impact polystyrene (HIPS) is used to achieve even further cost and weight reductions while maintaining the strength of the slatwall extrusion and assembly.