From left to right: Small Lock, Big Lock, Huge Lock and World Lock.
Locks are items which can restrict specific areas to specific people, determined by the owner of it. Locks come with a multitude of features allowing you to have control of locked areas. Locks can be used for private use or can be shared with others. There are several locks available to users through the Store. Each lock varies in price according to how much can be done with that specific lock.
The locks have multiple features that they all share. These are some of them: adding users to lock and setting to public. Adding users to lock allows a person you specify, by tapping/clicking them, to have access. Setting a lock to public allows anyone to build or destroy blocks within the locked limits.
Ignoring Air is a feature which allows you to control what is locked by ignoring spaces that are empty and locks only blocks that are connected to the lock.
The Small Lock locks up to 10 spaces.
The Big Lock locks up to 48 spaces. (The thumbnail in the Store incorrectly says it locks 50 spaces)
The Huge Lock locks up to 200 spaces.
The World Lock locks a whole world and allows the use of Sheet Music in the world. You can add users and set to public, as well as disabling Sheet Music or turning the Sheet Music invisible (this includes other type of musical blocks).
The Diamond Lock does the same as the World Lock but it is more stylish and it is made of diamond.
Small, Big and Huge Locks can be broken if the owner and all players who have access on the lock are not on for 180 days.