This is the Str8-Up fishing platform.  Allows you to stand securely at 9.5" above deck on the square model and 10" on the pedestal model.  No more standing on your graphs. Both have a 13"×13" platform for standing.
Both have a base that is permanently secured to your deck with provided hardware. Whenever it's not in use, just remove 2 thumb screws and take the mount off.