I've also been seeing metal security curtains temporarily pulled across the aisle, so that the cockpit, the restroom, and the front kitchen are all behind a metal curtain, sort of like this:

http://www.windowanddoorsecurity.ca/img/SecurityCurtain.JPG

Most recently on a Logan-LAX United Airlines nonstop in February.

This allowed secure restroom breaks, as well as food service to the cockpit.