BYER OF MAINE Heavy Duty Swivel Hook with Adapter and Chain for Hanging Chair/Hammock Chair, Swivels 360 Degrees, Holds up to 250lbs This is sold with the adapter and helps you hang your Byer of Maine Swivel Hook when you dont have a 4 surface. The adapter reduces the required surface area to 1.5. This better fits the standard framing found in most American homes. The adapter uses both the hardware provided with the swivel adapter, as well as a few pieces that come with the purchase. Installation is easy and intuitive. However, if you are uncertain, consult a professional for assistance. This adapter is 8 1/2"L x 4"W Though designed to be used indoors, this hook can be used outdoors with appropriate maintenance. Please be aware that the Byer of Maine Swivel Chair Hook and Adapter are designed for use in residential leisure applications to provide support for a hanging chair. They are NOT designed for use in therapeutic care or other commercial or institutional environments where they would be subjected continuous movement, rotation, or excessive repeated loading.