On last year's New Yankee Workshop, Norm built cabinets with what looked
like about an inch of scribe material on the sides (that is, the side
edges went beyond the 1/2" back by about an inch). The 1/2" backs were
to be screwed directly to the wall.

I'm not well versed on scribing techniques, but is the idea here to
remove most of the scribe material so the sides meet the wall tightly,
while the back is as close to the wall as possible?

I would think that a space between the back and the wall would cause a
screw to deform the back (think of a screw pulling the back toward the
wall as the screw is drilled into the cabinet back). I imagine the
ideal spacing between the wall and the back where the screw goes would
be zero.

-Does one need to consider such a gap when cutting the scribe material?
-How much "gap" is ok for screwing through the back to the wall?
-Does one have to shim the gap between the back surface and the wall
where the screw goes? (I can't imagine that would be easy to do.)

Thanks for any input,
Chuck