[rapjr9]

The original Star Trek sets made a lot of use of gobos, patterned metal shadow casters placed in front of lights. You can see some uses of them in pictures here:

https://www.trekbbs.com/threads/mudds-gobos.276831/#post-113...

https://startrektour.com/photo-gallery/our-beautifully-recre...

and you can take the above tour and see them in use yourself. They were made of metal because the lights were hot. Some sources for them, if you want to play with your own, are old metal pot holders and small cast iron table tops. They usually welded a rod to them to attach them to the light fixtures using standard lighting rod clamps so they'd be stable. Cast iron is heavy, aluminum pot holders are preferred and they disippate heat better.