On superbowl sunday I built the fence gate frame out of pressure treated 2 x 4's.
Yesterday I hung it in the opening. I sat it on top of a cooler to lift it off of the ground.
Before I attempted to mount the gate, since I was working alone, I screwed a piece of 1/2" plywood to the vertical leg of the gate. The width of the gate is one inch less than the opening in the fence. By using the 1/2" plywood as a shim the gate would be centered in the opening.
I used the plywood like a flange to secure against the fence post and hold it while I attached the hinges and the rest of the pickets. I first clamped it in place to adjust the position of the gate. Then I used a few screws to secure the plywood to the post.
I had to bring the gate up flush with the existing fence pickets so that the gate pickets would match up and the hinges would line up correctly. At the top of the opening you can see the string that marks the top of the pickets. The entire fence is on a slight downhill slope.
Once the hinges were bolted on I removed the screws that were holding the plywood to the post. After I checked out the swing of the gate I removed the screws holding the plywood to the gate. It worked like a charm! A perfect half inch space on either side of the gate.
The final result...
About $820 or around $9 per linear foot (not including labor)