In order to keep your valuables safe, you have the option to lock your doors, chests, furnaces or any other containers using a Lockette sign.

How to use
To use, place a sign without crouching (do not shift) on the door, chest or other container to be locked. The sign will automatically lock to the user who placed it. Another option is to place a signpost on the floor directly besides, or on, a chest or other container to be locked. Enter [Private] as the first line. The player's own name will automatically be entered on line 2 as the chest owner.  Players can also type in the full names of two other users allowed to access the chest's inventory on lines 3 and 4.
Sometimes, a player might want to allow more users access than can fit on one sign. The owner of a container can add more users by placing additional signs beside the container with the heading [More Users] where lines 2-4 specify the names of the additional users. You can edit the users on previously placed signs by right clicking the sign and using the command /lockette <line number> <text> to change it.

Example: /lockette 3 username1

If you would like to allow everyone to access a container, you can add a line with [Everyone] to the sign. Keep in mind though, this means anyone can access the container!
Note: that this means that nobody can break the sign, even the person who placed the sign.

To protect a door, you can use the same method as protecting a container, the sign will attach to the door automatically. In addition, you can attach a [Private] wall sign to any side of the blocks just above or just below a door. For double doors only one side needs a sign.

Once a door is protected it will only open for someone listed as a user and will not respond to redstone power or switches unless [Everyone] is listed as a user. Iron doors which usually won't open from clicking will work just as wooden doors. In addition, double doors will open together automatically!

You can also use [More Users] signs as with containers, with the caveat that the sign cannot be placed on the block above the door if the [Private] sign is not above the door as well! (This is done to prevent a security uncertainty issue.)

Protected doors will be closed automatically if a timer is set. A timer can be set globally with a configuration option, or individually for each door by using the tag [Timer: #] on line 3 or 4 of the [Private] sign, where # is the number of seconds that the door should remain open. If the timer is set to 0, this means the door will never automatically close.