Scale focusing refers to focusing which is done utilizing the distance scale and DOF markings on a lens (or distance scale and a printed DOF table, etc.) instead of using a split prism, AF sensor, or rangefinder to focus on something.
Remember, scale focusing ahead of time is always faster than autofocus or manually focusing on the subject.
If your lens has no distance scale, buy one that does. The old 28mm f/3.5 lenses are cheap and good for scale shooting.