VTurboWay 2 Pack Marine Grade Nylon Bimini Top 90°Plastic Deck Hinge with Pin and Ring, 316 Stainless Steel, Free Installation Screws

Combined with an eye fitting for your desired mast diameter, this is a great solution for building a collapsible bow-mounted kayak sail. When not in use as a mast hinge, it makes a great extra tie-down point for gear.