Switch stacks are the primary parts of electro-mechanical pinball machines, triggering game activity. I go over in this video, how they work, the different types of switch configurations, and how to clean and maintain them so they work reliably.
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On many games such as this Theater of Magic, there are stand-up targets in the middle of the playfield that take a constant beating from the ball. The switch blades in these targets, as well as the entire assembly will often get bent out of position and stop registering. I demonstrate how to use a simple tool to fix the leaf switch blades and put them back into position, as well as some other techniques for making sure the targets are solidly-attached to the playfield.
Stand-up targets have changed very little over the decades so this technique works on both old and new pinball machines.