Porcelain Donut Insulators are used to create corners in electric fence. They work best with high-tensile wire or poliwire and can be used on t-posts, wood posts, and metal posts. Made from high-quality, fire-resistant porcelain for long life. To install, thread the support wire around the groove on the outside of the insulator, and run the fence wire through the center of the insulator to create a corner.