It is amazing how many people MISSED THE DAMN POINT.
The original posted "trick" involves a situation where there are *no*
threads left in the wood. By backing the screw out with a little
pressure, eventually the wood will give at the point where the
original threads were, due to how the fibers of the wood remain (not
crushed, but cut). All this happens at a scale pretty much too small
for the unaided eye.
MInd you, the new wood screw will hold, but not well, because there
just is not much good fiber left. This trick does not really work with
metal - no fibers, obviously.
This is *not* the same "everyone knows it" trick about backing out a
screw to find the thread.
--
Will