The picture I posted above is of a brand new from Classic Parts horn switch that I installed in my '52 eleven years ago. It didn't work when I installed it. After a little investigating, I found that someone in the factory in whatever 3rd world country that made it didn't understand that the very nicely painted black piece was supposed to conduct electricity to the bare metal bottom piece when the horn button was pushed. I pinched a piece of 240 grit sandpaper between the two pieces and sanded off the black paint. Been working well since.

'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.