lock yourselves in

[JACEK1]

Hello.
Suppose that you are leaving your guests at home and they are going to stay at home all day long.
You advise them to lock the door from the inside.
What do you call this activity and what do you say to your guests - lock yourselves in!?
Thank you.

 

[teechar]

lock yourselves in

That's possible, but it sounds as if you're telling them to trap themselves.

I would say:
"Lock the door behind me."