How do I use the "z-axis"?

[BWDHarvey]

I noticed that when you move forward and back in edit mode, there are sometimes anchor points that become available.  This is kind of a depth, or "z-axis" I suppose. How do I get structures from ahcnor points in different planes on this z-axis to connect? I believe this is crucial for the next contest!

[mendel]

You switch Z-coordinate (i.e. move the editing plane F/R) while the strut is still "hanging" off your cursor.
Step by step:
1.) click on a joint. You should now have a connection from that joint to your cursor.
2.) Switch z-plane by pressing R or F
3.) Click to create a connection between the planes.

Tip: Pressing "shift" while clicking (creates a bar, but you retain the connection from the original joint to the cursor) can save you a lot of switching back and forth if used wisely.