Turn off the electricity both at the snap switch and at the knife switch.
Cover the blade of the knife switch with a fold of paper and close it.
Connect two heavy insulated copper wires, about No. 12, to the sides of the knife switch just as you connected the fine wires.
The knife switch L is fastened to the bottom of the case so that the handle will project through a slot in one side of the box.
Omitting the knife switch we have two three-way switches controlling the light.
If the knife switch blades are hard to move, look for cutting at the pivots.