The following are instructions on how to scribe distressed beams.
1.) Lay the beams together as shown, at the exact position they will meet.
2.) Spread the compass an inch or so. Hold it flat and slide it up along the beams as shown, so the point follows the surface of the main beam while the pencil draws a line on the butting beam. Do this all the way around the top and the other side.
3.) Next, you will cut down the line made from the compass. Tilt the jigsaw shoe to an angle of 10-15 degrees, so that you'll cut away more material towards the center of the beam. You can also use a coping saw (holding at the same angle).
4.) Test fit the beam.
5.) Remove any high spots with a coarse file.
6.) Test fit the beam again to see if any more filing is needed.
7.) Paint the cut end of the beam to prevent any possibility of raw polyurethane showing through a crack in the joint.
8.) After the paint dries, caulk the ends of the beam to close any small gaps.