Lock makes you lock a container with a key. The container can be in a room or in your inventory. The key must be in your inventory. Several circumstances will prevent you from locking a container. Perhaps the container has no lock, or the container is open and must be closed first. Once locked, it can be unlocked with the same key.
EXAMPLES
"lock old iron chest with old key"You: You lock an old, iron chest with an old iron key. Anybody: Hotblack locks an old, iron chest with an old iron key.