Otsukaresama desu.

I would like to be able to rotate an object by using the edge of another object as the axis of rotation.

Currently, I am using the LOCAL function to do this by estimation:
  
1. I relocate the origin of the object by snapping it to 1 point of the edge that I wish to use.
2. I manually rotate the local origin so that one of the axes (x, y, or z) is aligned closely to the edge I wish to rotate against.
3. When satisfied, I do a local rotation of the object.

This is generally okay.  However, it is difficult to do the manual alignment and the results are not always perfect.

Is there a better way of doing this?

Ijou, yoroshiku onegai itashimasu.