Denso starter solenoid with access plate removed:
Plunger pulls straight out, there is a spring beneath it. Don't lose it.
Here are the contacts. The plunger is pulled down by an electromagnet to make the connection between the positive battery cable and the starter motor itself and it also pushes out the starter drive to engage the ring gear. This happens when the small wire is energized when you turn the key to 'start'. Battery cable connection is on the left, solenoid engagement wire beneath it, start motor wire on the right.
It's the side contacts that wear out unevenly. If you could look at this one, you'd see one side is obviously thinner than the other. This accounts for the intermittent no-start and repeatedly hitting the key eventually makes it start again. Also why a jump from another running car makes it work better since you are getting 14+ volts from the other car as opposed to less than 12 when cranking normally. The extra voltage pulls the plunger down harder helping to make contact.
Go ahead and take one apart. It will become painfully obvious how these things work when you do.
If con is the opposite of pro, Congress must be the opposite of progress.
Ineptocracy (in-ep-toc'-ra-cy) - a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers. syn- socialism.