This set of Field Guardian Wood Post Screw-In Corner Electric Fence Insulators has a strong steel bracket with a self locking nut that holds the round donut insulator. The insulators are used for corner and end-post applications for all sizes of polyropes, hot coat, polywire, and low tensile wire. They feature a wheel-like design that allows the tensioning of the rope to allow you to adjust things to your liking. A deep wheel groove helps the screw-in insulators hold rope secure for consistent and reliable operation. These electric fence insulators are easy to set up as well, given each one has a built in screw that you use to attach them to a wooden post.