Me and my friend are in a skyblock together and when we place something like a chest or a furnace it says its private is there anyway to remove that?
This section of the command reference will tell you every command used for chest protection: http://www.sandlotminecraft.com/pages/commands/#chest-and-door-protection-2
The person who placed the chest should type /cremove and punch the chest, furnace, etc. Additionally, you can use /cmodify (player) and punch the chest so that both of you have access. Good luck!