Lock
The Lock is a modded item that is craftable on Nguhcraft and can be used together with the Key to lock chests.
Crafting Recipe
A lock can be crafted using iron ingots and redstone.
Pairing
When initially crafted, locks are initially unpaired. Unpaired locks have no enchantment glint and their item description is empty. Unpaired locks have only one use: they can be paired with a Key by putting both of them in a crafting grid in any position. A lock that is paired with a key will display the key’s id in its description.
A lock can be paired with a key even if it is already paired: the old pairing will simply be removed, i.e. the lock will only be paired with the new key.
Locking Containers
A paired lock can be applied to a container[1] by using the lock while sneaking[2]. This will consume the lock and make it so the container can only be opened if you have the corresponding key.
A locked container is treated as an unbreakable block: it cannot be mined, destroyed by explosions, moved with a piston, etc. The only thing you can do with a locked container is open it, provided you have the corresponding key.
A container can only have one lock, and it is impossible to apply a lock to an already locked container.
For info on how to remove locks and open locked containers, see here.