Lock

A silver key can open an iron lock

Do you lock the front door at night?

It’s got a lock to it

Lock the door on your way out, please.

lock, stock, and barrel

to lock horns

to lock someone up

To lock the barn/stable door after the horse has been stolen.

to lock up money

to pick a lock

under lock and key

under lock of key

You forgot to lock the door.