Making the first cuts

So I have all my fabric, and the really cool Olfa cutting mat (from Hobby Lobby with a 40% off coupon) has been joined by a really cool Olfa rotary cutter and (yep, you guessed it) really cool Olfa rulers (that I got on a wicked good sale from Connecting Threads.com). I'm all set now, right???

I am trying to remember why I got a 6 1/2" right-angle triangle ruler though. There are no diagonal lines anywhere in this block--unless I cut something WAY wrong....