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.
In this video he builds a dandy folding step stool.
Ok, lets add this too.... A small walnut stool with very interesting joinery.
And I really like how he made a stationary work bench, mobile.