In single- and double-prong versions, String's add-on Vertical Hook is designed to fit the back panel of the freestanding outdoor shelf. Whether it's garden tools, grilling implements or any other accoutrement to outdoor activities, the hanging accessory helps keep things conveniently organized. Made of stainless steel to withstand all types of weather and sea air, the single hook comes in a package of 4 and the double in a package of 2.