20. Nail outer frame together

It is time to nail the boards together, but first, add a dab of wood glue at the end.

To use the gun, all you do is:
1.  Place
2.  Push
3.  Pull the trigger.

Before placing the gun, secure the boards under your knees.  Be picky about getting the corners flush together, and weird spacing will result in a crooked frame. 

Use two nails on one side, and one nail on the other.
Wipe away excess glue.