How to align two differently rotated objects to be exactly side by side can anyone tell me the best way to exactly align plane 2 to the side of plane 1 in this blend file. It's like they are 2x4 lumber. Imagine plane 1 is in a fixed position, and my task is to line up plane 2 exactly side by side to plane 1. I made all the locations and rotations random just to see the best way to align
plane 2 with an arbitrary location and rotation of plane 1.
Thanks for any ideas for me to try.
Here's the .blend file:
Since these object's local axes are both aligned to their meshes, you can use standard align and snapping tools.. in 2.8, all in Object Mode:


Create a Custom Transform Orientation from the target (stationary)
object. (Orientation dropdown in the header, '+' with target
selected)
With the source (moving) object selected, Object Menu > Transform > 'Align to Transform Orientation'. Now your objects rotations should be the same.
Move the source object roughly into place, and with Snap (ShiftCtrlTab) set to 'Vertex', 'Closest' , with Align to Rotation switched off, snap the source object into place. 


2.8 has lost a lot of standard keymaps, which makes this harder to describe than in 2.79.