How does it work?
When you place chests other containers they are automatically protected from other people.
As long as a chest is protected, nobody can open your containers. They also can't be pulled from using hoppers, so your items are completely safe!
In order to allow people to access your chests, use the
/trust command in chat to trust them. Trusted players will be able to open all of your current and future containers.
In order to make a chest accessible to everyone (for example a public chest for a farm), use
/cmodify public and then left click the chest.
likewise, you can use
/cmodify private to make a container private again.
/chopper to allow hoppers to access a container.