A Garage Door Makes a Precision Reference

I was looking at my garage door one day and noticed the stiffener channel running the 16 foot length (4.88m) seemed to be rather straight, so I put up a string line to see what it may be and found there was only about a 1/16” dip (1.59mm) over that distance. Very impressive I thought; that is more than satisfactory to use as a straightedge gauge when inspecting and sorting planks for cutting & jointing purposes

Crook and bend show up readily against the channel and their area, dimension, and location can be precisely marked out.

Edge wane can also be detected and calculated for determining overall useable lengths in a workpiece as well.

Using the findings, I set about the task of truing up one side of some nominal 2 X 6 x 8 ft. stock (38.1 X 140 mm X 2.44m). In the image I shimmed this end of a crowned board to fair it up for attaching a temporary straightedge:

Next I attached the straightedge that will ride against the saw's fence, making sure it was in full contact with the channel.

Finally, I ripped the workpiece on my radial arm saw to a smooth and flat edge and removed the guide board. To finish, I then ripped off the widths that I needed for my project using the newly established straight edge, and crosscut them to length.

This method now saves me the difficult process of truing up one edge of a long plank to use as a gauge for its companions, and the door rail is, of course, always available and self- storing.