lock down

To secure (something).

To blockade and lock (e.g. a building or campus) so as to prevent ingress or egress; to make the occupants (of an area) stay locked indoors for their safety.

To limit the use of (a computer network) to only users with permission.

To make (an arrangement) secure, definite, or permanent; to fix.

To cause (another person) to enter into an exclusive romantic relationship.

To travel through a flight of locks on a waterway in a downhill direction.