Interface Builder. How do I toggle between open projects using a keyboard shortcut?

Can someone please remind me how do I toggle between open projects using a keyboard shortcut? I briefly knew how开发者_高级运维 to do this but it has evaporated from my brain and Google is no help.

I don't know what the shortcut is for switching between open projects, but in OS X in general you can use Command + ` (backtick) to cycle among windows of an application.