13.10 Beta 3 - Lock my screen?

So, I'm a new Pinguy OS user - not yet 24 hours. I'll post another thread in one of the other forums gushing about how great it is (and it is!), but first -

I have noticed that neither super-l nor ctrl-alt-l lock my screen, and I don't see an option in the menu to lock it, either.

I'm guessing this has something to do with the MDM switch?

But regardless of that - I assume I *can* lock my screen, yet can't figure out how. Can someone please help me out? Thanks!