I don't know why but when i place a lawn chair in my LAN world the other person can't see it.

I'm hosting btw. Also after testing it a bit more when they place it I can see it and sit in it

Does this problem still exist for you @queenofmillers ?

Closing due to author unresponsiveness.

Both clients need to install the mod, if your friend doesn't have the mod installed then he won't see the mod content.