Ply Gem vinyl siding mounting blocks create a smooth, stable surface for installing accessories on your home — from lights and doorbells to electrical outlets, water faucets and more. Constructed from high-performance polymers, our siding mounting blocks withstand extreme weather and hold their color for the life of your home. Most Ply Gem mounts feature a two-piece design that adjusts for easy installation over all types of siding. Ply Gem universal siding mounting blocks are ideal for installing large items such as lighting fixtures, house numbers and mailboxes. The picture-frame design adds interest and lends a finished touch. You can choose from several sizes and styles, including square and rectangle shapes with gently rounded and scroll-cut corners.