Earl, that's using your noggin'. Great tip, the picture explains it all. I moved this to Tips and Tricks, so it will be more easily found by those jointerless or jointer challenged folks looking for a way to get a good straight edge.
I have done the same thing at times, although I have a very good 6" jointer. But one thing I have done is to make a 8' jig so I can use my router to edge joint a long board that may be too cumbersome to run over a cabinet model. It is also handy with I am away from the shop. I simply took an 8' piece of 1/2 plywood about 6" wide. I then took a piece of 1/4 plywood and attached it on top of the other piece. Simply run the router down the straight edge and you have a perfect straight edge and will always know exactly where to clamp the jig for a cut.
Jim in Mayberry