Bottom part of a post used for surface mount applications — i.e. where your post is mounted on top of an existing hard surface (vs cementing the post in ground). We carry 2 types of flanges: 1) Deck Mount. Which are available for 2″ and 2.5″ posts only. The Deck Mount is not available for use with Style 3 with bottom rail lowered, Style 9 or Style 10 because the expansion bolt obstructs the bottom hole in our prepunched posts. 2) Welded Plate. Available for all post sizes and all fence panel and gate styles. Unlike the Deck Mount which is a 2-piece configuration, the welded plate option involves a plate being welded onto the bottom of each post at our factory prior to powder coating. The welded plated post is a 1-piece configuration.