/messageblock

When used, the next block you place is a message block.

• Message blocks cannot be broken without commands.

Attempting to break a message block will result in the block’s message being displayed to a single player, or all players if /say is used. You have to enter the message before executing the command. The ‘|’ symbol is used to separate commands.

• Supported blocks: White Wool, Black Wool, Air, Water, Lava.
• Message blocks cannot flow.
• Entering air message blocks, water message blocks or lava message blocks will result in the block’s message being executed.
• Message blocks cannot be pushed by pistons.
• Message blocks cannot be blown up or burn away.
• The alias to this command is /mb.

Command syntax: /messageblock <block> <message>