Gauge blocks work great for quick, accurate biscuit joiner fence settings.
All you do is pinch the block between the fence blades. This technique
will also ensure the fence is set parallel to the blade. Joiners with
rack-and-pinion fence adjustments automatically set the fence parallel
with the blade. For this type of joiner, use spacer blocks between the
fence and a flat surface-like your benchtop-for rapid fence settings.
Gauge blocks are also handy for cutting double biscuit joints. Cut
the first slot with the joiner base referenced off the work surface.
Then, use a spacer block under the joiner base for the second cut. The
gauge block eliminates the hassle and confusion of flipping your stock
or resetting the fence. Make a whole set and you'll be covered for any