An apparatus for adjustably securing a boat accessory to a boat. A first member has a plug and a second member has a socket. The plug has a rosette shape with rounded protrusions and the socket has a corresponding mating shape. Both the plug and the socket have openings for a fastener to secure the plug in the socket. The first member is one of a mounting base and an accessory base, and the second member is the other one. In one embodiment, an extension is positioned adjacent the plug so as to separate the first and second members. In another embodiment, the extension has a plug on each end and the first and second members have sockets. In another such embodiment, the extension has two members joined with a rosette-shaped plug and socket.