The wood is first utilized, but not visually seen, when Galdino was seemingly floating in the water-filled Rain Dinners underground meeting hall, with a piece of the wood underneath him, which would prevent him from sinking by his Devil Fruit weakness.
The kana for "Kuuigosu" is backwards for "sugoi uku" (すごい浮く,"sugoi uku"? literally meaning "Floats Unbelievably").
In the anime version of where Galdino was on top of water, since the respective SBS had yet to come out, and therefore the wood's existence had yet to be explained and was not properly seen, it was replaced with a table to avoid what seemed to be a contradictory scene.
↑ 1.01.1One Piece Manga and Anime — Vol.
66 Chapter 653 (p. 19) and Episode 573,
Franky explains to Usopp about how Kuuigosu is used to ascend from Fish-Man Island.
↑One Piece Manga — Vol.
19 Chapter 175 (p. 19),
Galdino seemingly floating on water despite his Devil Fruit curse.
↑SBSOne Piece Manga — Vol. 25 (p. 86),
Fan question: Mr. 3 has Devil Fruit powers, so how come in volume 19, page 185, panel 3, he's floating on the water?
↑SBSOne Piece Manga — Vol. 66 (p. 142),
Fan question: [...] Then, I suddenly remembered about the "piece of wood that floats unbelievably" that made Devil Fruit user Mr. 3 float in the water after being K.O.ed in the Alabasta Arc; could it be that you were talking about this back then?! Well?!
↑One Piece Anime — Episode 109,
Galdino was on top of a table to avoid confusion of this seemingly contradictory scene.