This hat bracket is an ideal replacement for your boat trailer to be used to mount your Guide Poles. Made out of 1/8 thick galvanized steel, it is normally used with an Upright guide pole set. It is designed to clamp 1 1/2" x 1 1/2" square tubing to the main frame of a boat trailer. This bracket has multiple holes for various size frames (widths) and uses 3/8 diameter U-bolts to attach to your boat trailers frame. To determine the correct U-Bolt needed to mount this Hat Bracket and your guide poles back to your trailer, measure the height and width of your trailer frame where you will be putting the bracket. We have many Boat Trailer U-Bolts available in many lengths and widths. You will want to select a 3/8" diameter size, as the pre-drilled holes in this bracket are designed for 3/8" diameter U-bolt.