I don't doubt it cuts in both directions, but it's not the cleanest cut.
Another consideration is the miterbox holds the board on the push
stroke.  During the pull stroke, it would need to be held either with a
clamp or the user's thumb.  The force on the pull stroke may be more
than you would want to hold if the saw were cutting.
-- 
Erik von Sneidern
www.disstonianinstitute.com

On Thu, 2012-08-23 at 12:06 -0700, Jim Crammond wrote:
> You don't pick up the saw from the wood on the back stroke when using
> a miter box, so why not cut equally in both directions? 

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