trying to figure out the factory light switch. the shaft with the knob seems to want to insert at a slight angle. when you raise it up into the center of the opening, this is what seems to allow the notch at the end of the shaft to catch in the internal latch which allows you to pull the switch forward. when you relax the shaft, allowing it to be offset a bit on the opening, the internal catch releases, allowing you to remove the shaft again

there is a set screw in the bottom of the knob. I'm thinking you're supposed to take the knob off, insert the shaft into the opening at a slight angle and then attach it to the dash using the nut/collar, which then raises the shaft into the center of the opening, thus allowing the notch in the end of the shaft to catch on to the latch inside the switch. otherwise the shaft just pulls out and never catches inside the switch.

i've removed the set screw, but cannot seem to remove the knob. tried placing the shaft in a bench vise and carefully tried tapping the back side of the knob off using a screwdriver wrapped in a towel and a dead blow hammer. only managed to bend the shaft. any better ideas on how to remove the knob?