The Command Block is a block made with the intent to support Adventure mode and allows mapmakers to expand the interaction with the player through server commands. The block can run specified server commands when activated by a redstone current. Considering its great power and possibilities, it can't be normally crafted. Currently, it is not available in the creative mode inventory either. Only players with sufficient privileges to use the 'give' command: /give 137 can obtain the block. Furthermore, only players which are in Creative mode and are also an operator on the server are able to edit and successfully save the command of the block. To be able to use this block in multiplayer, you have to set the value of enable-command-block to true in the server.properties file. If this line doesn't exist, you'll have to add it. When you are in survival, you can break the command block with a single click, but it doesn't drop anything. When you break a command block with a pickaxe, it will drop. They can't be pushed by pistons, as they have tile entities. The maximum command length is limited to 254 characters.