I made one of these years ago, exactly the same and totally different! I have described it a bunch of times, but never got un-lazy and made some pics! MIne has wheels that roll on two rails, and a 4x4 in the middle that tilts like this, with the screw up and down.
love it because I can taper a slat from middle to end, flip[ it around and do the other side exactly the same taper.
Greaty work, man.