The original "blade retractor" was made purely for my own amusement and use.
I got quite a shock when I watched the Brian Boggs dvd.
The facility with which he makes adjustments while working, is awesome.
However when making a pair of Barnsley chair copies, I needed to take 1 thou" shavings from curved surfaces about 1 1/4" wide. This called for a similar setting to smoothing plane, i.e. slightly curved, "balanced" blade with very fine shaving. Not being able to see so well these days I find the retractor useful for these fine settings.
It satisfactorily solved my problem, but I can quite see that others may have no use for such a device! Which by the way was quite an effort to build. The idea was concieved in a few minutes but the making took much longer........
best wishes,
David Charlesworth