I've just spend the better part of an hour watching the youtube videos
of Matthias Wandel's tenoning, slot mortising and box joint jigs. I
think you can drill down from this site to get to the videos:
http://woodgears.ca/joinery.html.

To say that these are nifty, IMHO, is an understatement. Any of you
folks taken it upon yourselves to build one or more of these? If so,
what's your take on the level of effort? Any tips ... known gotchas and
the like?

TIA

Larry