Telescoping side rails for a pickup truck are extensible, hidden vertical pillars within each side wall of a pickup truck. The extensible vertical pillars are connected at the top by the side rail sitting atop the side walls. A set of telescoping pillars is added to each of the two side walls bordering the bed of the pickup truck. When extended, either manually or via a powered option, the vertical pillars, which are joined at the top by the side rail, form a skeleton structure of a tall side wall. The side rail is an added stabilizing connection. The skeleton structure can be used alone or with added horizontal beams inserted through horizontal access ports in the extended pillars. Preferably, the access ports allow passage of a standard 2×4 or other stake through the pillars to create added structural stability to each set of telescoping pillars.