Tips I've Learned: Juicing a Lime/Lemon

Of course I had to get one of these!

It's the best "juicing" tool I have found yet!  Here's the thing - I always thought the best way to use this tool was to face the lime/lemon this way:

But, while in a cooking class, I was told that the correct way is this:

I have tried both and I have to agree that it is less messy and more effective when the fruit is pressed inside out!