Edson's 992-35 Pivot Bracket attaches to 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 allowing it to fold down. Fold-Down Towers are perfect for trailer boats, low bridge clearance and end of the season storage. Use 989-1 Right Angle Base (sold separately) if mounting to a vertical surface and folding tower fore and aft.