"Nick Degidio" wrote in message
...
Maybe this is to late, but....

Joint 1st board, good side up (89 degs using your example)
Joint 2nd board, good side down, (91 degs. when flipped)
When joined, should be 180 degs

When I use my jointer, and do check for 90 degs, I still reverse the
boards
when edge joining.

Easier way it to trim it on the table saw, turn the board and rip it to
proper width and if the saw is properly set, you have two 90 degree sides,
no remembering what is 89 or 91.