I assume by narrow edge you mean like the 1” edge of a 1×6.
So, like Lee said, the board wants to look like a C.
You can’t do anything with this on a jointer but make it worse.
You need to attach this board to a known straight board of equal or greater length, in such a way as the bowed, or hooked high part of the arc is overhanging the edge of the carrier board.
Now, with the straight carrier board against the fence of the table saw, and the fence to blade distance set to just let you rip off the high part of the crook.
After you have one edge straight line ripped, then you can remove from the carrier and put the new straight edge against the fence and rip the other edge to be parallel.
What you are left with is a narrower straight board.
-- Michael :-{| Diapers and politicians both need to be changed often; and for the same reason.
