Boat Seat Hardware I Am Trying To Put Swivel Bases So I Can Put A Boat Seat On My 14' Alumunim Boat?

I am trying to put swivel bases so i can put a boat seat on my 14' alumunim boat? - boat seat hardware

I have a boat of 14 "Aluminum and those who, like seats on the boat and his head with foam just below ..... there is no way to use a screw and a nut .... What kind of screws or Bolt Is it necessary to use screws to leave pivot bases, not to be?