C.e. Smith 27600 Bunk Board Guide-On - 5 in.Carpeted bunk boards provide proper center loading even in wind or side current conditions. Adjustable boat guides can be fine-tuned to work with your boat and your trailer. The pre-galvanized steel support posts mount horizontally on top of or below your trailers frame rail. Just slide the posts into the boat guide supports and secure the posts so that the distance between the bunks correctly matches the width of your boat. The bunk boards then tilt to conform to the boats hull. Guides will help to center your boat during loading and to hold the boat during transport.Features. 1.5 in. square pre-galvanized uprights angled out at 75. 2 x 4 x 60 in. boards tilt to hug the hull and are covered with high grade marine carpet. boards are untreated Southern yellow pine. Height of 21 in. with adjustment out to 13 in. from frame on each side. Can be mounted on top of frame for extra height. Complete with mounting hardware to fit frames up to 3 wide x 4.25 in. high1.5 in. square pre-galvanized uprights, angled out at 75°2 x 4 x 60 in. boards tilt to hug the hull and are covered with high grade marine carpetboards are untreated Southern yellow pineHeight of 21 in. with adjustment out to 13 in. from frame on each sideCan be mounted on top of frame for extra height