This screencast demonstrates how to create a squarewave in The Foundry’s Nuke. You’d want to use this if you ever have to toggle a switch on and off repeatedly at set intervals, for example.

We basically loop some key frames in the curve editor. The looping technique can be adjusted for many other applications.

If your brother’s name in Nick, I made this just for him.

The video is more easily viewed in fullscreen – click the button in the bottom right of the player controls.