If mounting your radar mast to a vertical surface use Edson's 989-1 Right Angle Base. This attaches to Edson's 992-35 Pivot Bracket (sold separately) that allows your Radar Mast to fold down using Edson's Fold-Down Adapter for Radar Masts (990-23, 2 3/8 in Mast & 990-35, 3 1/2 in Mast) (sold separately) that is secured to the bottom of your radar mast. Fold-Down Towers are perfect for trailer boats, low bridge clearance and end of the season storage.