What is an 'eccentric' bolt?

In mechanics, an 'eccentric' isn't a nutcase billionare - is something that has an off-center hole in it. For example, take a small wheel, with a mounting shaft run through it. In a regular wheel, the shaft runs through the center. An eccentric wheel is just like a regular wheel, except the shaft doesn't run through the center; it runs through an off-center hole.

An eccentric bolt is usually a bolt with a collar on it. The bolt shaft is tapered in the middle to run through the collar, so the bolt is thinner in the middle and thicker at the ends. The collar has an off-center hole in it and is free to rotate.

As can be seen in this sketch, an eccentric bolt allows adjustment through rotation. As the bolt assembly is rotated, the collar moves further off-center. This property is what makes eccentric bolts useful for adjusting and aligning different connected parts. They are frequently used in DSMs and other automobiles for suspension adjustments.

See also: https://en.wikipedia.org/wiki/Eccentric_%28mechanism%29