Several years back Bridge City Tools manufactured and sold a Kerf Maker,
a dandy tool for cutting dado's and grooves perfect in width with
undersized blades and router bits. I own one and it worked extremely
well for cutting 3/64" deep half lap joints 1/2" wide with a 3/8" wide
dado set.

This guy builds one and may have had too much coffee before he began
filing and sanding.

https://www.youtube.com/watch?v=YsfOWa_TFR8#t=198

In this video he builds a dandy folding step stool.

https://www.youtube.com/watch?v=r8iCJZQvFiE#t=198

Ok, lets add this too.... A small walnut stool with very interesting
joinery.

https://www.youtube.com/watch?v=aa6cYgxLMkE

And I really like how he made a stationary work bench, mobile.

https://www.youtube.com/watch?v=RRpVr4nwt9g