This entry covers the simple approach of aligning two objects along a reference side. This can play an important role when building a mesh that will be 3D printed and you want to make sure the bottom layer is perfectly flat and aligned.
The short explanation is to use the Align Objects command and set the Align Mode and axis.
For this example, I was making a keychain with a loop for a connecting. I made two objects, but I needed their bottoms to be aligned perfectly.