Originally Posted by steveo

Saw for cutting plugs or other parts flush with a surface without maring the adjacent surface. The saw has tooth kerf on one side only and is very flexible so as to contact only the surface to be cut flush with remaining surface. Mostly used to cut plugs (however real router users use a router to perfectly match the surfaces without maring adjacent surfaces, set the router bit a couple thickness of paper above the surface adjacent to the plug, and turn on the router !)
steveo