What does diagonal arrow key mean in MacOSX?

Hi,

When I use IntelliJ on my MacOSX, it suggested one of this keyboard shortcut when "No files are open" in a project:

Now I know the first one is the "Option/Alt" key, but what is that second key suppose to be? How do I type that?

I've checked the http://www.jetbrains.com/idea/docs/IntelliJIDEA_ReferenceCard_Mac.pdf and I don't see that diagonal arrow key there.

Thanks,

Zemian