In MMD 160920 Luke Myers was looking for someone who dares to play a
roll backwards.  Backwards is not the only way to change the direction;
flipping left and right is the other one.  So there are four (4)
possible commutations.

But why the hell I am telling this again?!  Everything has happened
before, even in the history of the MMD!  So I point Luke and all other
interested readers back to the MMD Archive:

http://www.mmdigest.com/archives/Digests/199701/1997.01.24.03.html 

Best regards from Germany,
Walter Tenten