catwalk

1. A narrow, suspended structure, usually ~3' wide with railing on both sides, used as a lighting position, gallery, or to provide access for the servicing of equipment or machinery.
chcc_catwalk_lighting.jpg
http://www.jordanaudio.com/CHCC_worship_center_project.htm
Since in some theatres, it is the only FOH lighting position (aka beamslot, cove, ante pro) often called simply "THE catwalk." Others however, like larger black box theatres, may have many catwalks.

Video filmed in the catwalks of The Santa Fe Opera during the 2009 season. Disregard the sparkly wrenches and other accoutrements.

http://www.youtube.com/watch?v=Z2SKhRPq6gk

2. In the fashion industry, synonymous with runway. "I'm too sexy for my shirt, on the catwalk, on the catwalk.