We made a "REC" sign so people don't enter the studio while we are recording voices or foley.
We used a a 3D printer to create to pieces: a box with a hole to hang it on the wall, and a cover that holds by friction.
Then we just had to stick a puck light with a remote control in it, and glue a semi-opaque sheet on the lid to filter the light.
You can download the .stl file here. Commercial use not allowed.
