I happened upon this ebay auction today in which the seller lists some black castle corner wall pieces.  Get this—he has both left and right versions of this castle wall corner piece!  I'm surprised that he didn't list the flat wall pieces as north-facing and south-facing.

Sometimes the things that nonLEGO people call LEGO pieces just amaze me.  I've seen people call plates "flats," and I've seen them call tiles "smooths."  I'm not even sure how this ebay seller determined weather each piece was right or left handed.  It reminds me of the time that a manager from another department sent a new guy to our department to get an English size crescent wrench and a metric crescent wrench.

Funny stuff...

David