Lock the door please

Lock the door please
 

I'm parking my car, which has non-electric door locks, and asking the passenger to lock his door as he gets out - so I won't have to reach across and do it myself.
"Ciérrala bajo llave" wouldn't work, so what should I say?

I have said, and it worked) something like: acerroja la puerta--baja aquella palanca. There's probably a better way of saying it, though.

In Mexico: "Pon(le) el seguro por favor". :)