Steps:1. Decide where you want the gate, then remove a picket to expose the support post closest to that location.
2. You'll need a 40-inch opening for the gate, so measure and mark a point 40 inches from the post and mark the location. Remove the picket at and mark the point on the horizontal support beams. Be sure to salvage any pickets that are in the way before cutting.
3. Put on safety glasses and dust mask and cut through the fence supports (figure A).
4. Remove the section of fence and put away in a safe place (figure B).
5. Rake the area to clear out any undergrowth and debris.
6. Dig hole for new fence post using posthole digger (figure C). Dig the hole deep enough to bury about 1/3 of the post.
7. Tamp the soil at the bottom of the hole using the new post. Lay about an inch of drainage rocks in the bottom of the hole (figure D).
8. Mix cement according to directions. Center the post in the hole and pack cement in around post (figure E). Tamp cement down with the end of a 2x4. As the hole is filled, mound the top of the cement so that water will run away from the post.
9. Tie a string from the new post to the existing post at the other end of the opening to make sure they are aligned properly (figure F).
10. Brace and stake the post to hold it in place while the concrete dries (figure G). Let the concrete set up overnight before installing the gate.
11. Measure the opening and transfer measurements to 2x4 frame pieces. Use a carpenter's square to draw a perfect line for the cut.
12. Cut lumber with circular saw. Be sure to wear safety glasses and a dust mask when working with power tools.
13. Select a one-piece hinge and support bracket for easiest installation and to help prevent the gate from sagging later (figure H).
14. Attach the brace/hinge to the bottom 2x4 frame piece by first pre-drilling the holes and driving in lag screws for better holding power.