Knife/spoon in FF4

what do I have to do to get it?

You get at least one of them when you visit Yang's wife Fabul later on in the game. I think you get the other one when you find Yang in the fairy world, thentell his wife and she helps to wake him up.

in the fairy world its good to have float,it is used with many stuff there(i think there were damage tiles and a monster that casts quake).Also there was many monsters that are hard

Make sure you do it BEFORE you go to the moon. Go to the Sylph cave in the underground, where you will find Yang. Talk to him and the Slyphs (he's unconcious) and then go to the upper world and speak to Yang's wife. She will give you the frying pan, take it and return to the Sylph cave, talk to Yang and the little item box will open. Select Frying Pan and smack him good with it. Then return to the upper world to tell his wife about it and return her pan (it's useless for anything else) and she will give you the spoon.

thanx man