Thanks to the patented cobra there is no longer any need to slide the cord onto the rail; it can simply be hooked on wherever you choose. The perlon cord is almost invisible and in combination with the smartspring it can bear a load of up to 9 lbs per hook. Balance larger frames or distribute the weight of heavier frames by either using two cords and hooks or by purchasing the STAS Zipper Hook + Steel Cable with Cobra. For more purchasing options view our full selection of products sold by STAS Picture Hanging. Product includes 4 cords 59" long and 4 hooks.