In one of the Tage Frid books, he gave some tips that for jointing 2
pieces, you can put the 2 pieces face to face, then use your plane
to smooth/straight the edge. Since the 2 boards are put face to face,
when you join them, they will match, even if the plane is not 100%
90 degrees.

Go find the book (library, bookstore, etc.)
Hope this helps.

Pinwu

Dr. Rev. Chuck, M.D. P.A. wrote:
Jim wrote:

I don't know how much effort is made
to make sure that the edges are exactly 90 degrees
to each other. If you are just using a joiner
plane all you would be doing would be continuing
the angle already existing on the wood. Before
electricity and jointers what did they do? Did
furniture makers clamp some type of fence unto the
board they were join planing? Or am I trying to
be overly precise on this.