This part models the cast iron brackets of the Climax Class A locomotive that were mounted on the frame and supported vertical wooden posts that were the frame for the cab. The part is designed to attach to a 3/16" x 3/16" square post using a #0-80 flat head screw on the underside. The post itself is mounted to the locomotive frame using a flat head screw, and then the post holder is slid on the bottom end of the post covering the screw through the post. To the observer, it looks like the post holder is attached to the frame and supporting the post. Take a look at the cover photo of the book, "A Climax Class A Live Steam Locomotive Model" to understand the part and its finished appearence. There is information on the book and the cover image at
http://model-shop.net.