For miter joints occurring at angles other than 90 , for materials of the same cross-section the proper cut angle must be determined so that the two pieces to be joined meet flush (i.e. one piece's mitered end is not longer than the adjoining piece).

The mitered end should slope toward the side of the board that will touch the building.

The mitered end should slope toward the board's rear surface, the side that rests against the building.

Hold it in place, aligned with the markings on the frame or extender strip, and make sure it fits flat against the mitered end of the top piece.

Then hold the molding firmly, molded face up, overhanging a bench or table top, and cut along the molding's profile to remove the mitered end.

In that position the bottom edge of the horizontal piece should rest on a mitered end of the brace.

Attach the patch piece by drilling pilot holes at an angle through the mitered ends of the patch and old fascia boards.

Another way is to install the moldings as is -with mitered ends at a 45-degree angle -then fill in any gaps that remain by using a spackling compound or wood plastic.

To use the flat board, press the molding against the top block so that the mitered end protrudes very slightly past the edge.