If you have gone to the trouble and expense of building a post-and-rail fence from wood, finishing it off with a wooden gate painted the same color makes for a pleasing and authentic final look to your fence. While the basic technique for building a wooden gate is about the same for any size gate, the materials you use will depend on the size of the gate opening and on whether you are trying to match the fence or not. We will presume a 10-foot livestock gate built of 2-by-6 inch material.
Measure the gate opening, making sure to factor in space for the hinges. If you want your gate to swing both ways, screw hooks and eyes are best. Simply measuring the exact length of the solid end of the screw hook may not give you enough room between the gate post and the gate for it to swing freely. Allow 3 to 4 inches of standoff. Likewise, allow at least an inch between the latch post and the gate so the gate does not bind.
Mark a 2-by-6 inch board to your measurement. To check the length, lay the board in the gate opening with one end an inch from the latch post and the marked end at the hinge post. Lay the screw hook against the hinge post as though it were already mounted to the depth you determined was necessary (some of the threads may be exposed). Check to ensure the mark on your board touches the outer, curved edge of the hook.
Cut the board and check it a final time before cutting your other boards to the same length.
Measure the distance between the top edge of your top rail and the bottom edge of your bottom rail and cut two 2-by-6 inch pieces to that measurement. These will be the verticals at either end of your gate.
Work on a flat surface to keep your gate pieces square. Lay out your horizontal fence rails with the ends against a straight-edged piece of lumber or a wall. Space them apart the same as your fence rails and measure the distance between them at both ends or use a level against the top edges so they are evenly spaced.
Carefully lay the two vertical boards across the ends of your rails, aligning the corners.
For best results, pre-drill holes in both ends of your verticals before trying to fasten them to your fence rails. Sink one carriage bolt or screw in the top rail, check your square, then sink a screw at the bottom and check your square again before drilling holes for the other rails.
At a minimum, tack each rail in place against the vertical pieces with at least one screw to hold the rails while you work.
To keep your gate from sagging you will need a cross-brace. Measure inside the vertical pieces diagonally from the upper corner at the latch end to the bottom corner at the hinge end.
Cut a 2-by-4 or 2-by-6 inch board with the ends at a 45-degree angle in opposite directions.
Fasten your cross-brace between the uprights as shown.
Drill holes to secure all your boards with at least two screws at each end. Carriage bolts are recommended for all corners.
A gate made of 2-by-6 inch lumber is heavy. To keep it from sagging, either set your hinge post in concrete or make the post tall enough to run a support cable from a screw eye in the top of the gate to another at the top of the post (or use both methods).
Find some concrete blocks or scrap lumber to hold your gate at the correct level while you line up your screw hooks. Align the top of your gate with the top rail of your fence.
Mark the gate post at the top of the gate. Mount the top screw eye in the gate's top rail about midway. With the gate standing in position, align the screw hook where it will catch the screw eye.
Mount the top screw hook in the hinge post and drop a plumb line to align the bottom one.
Drill a hole for the screw hook and use a wrench to screw in the hook.
Repeat the process of mounting the screw eye and hook for the bottom set. They are aligned to the middle of the bottom rail.
The latch can vary from a simple chain and hook to elaborate latch hardware. Choose your hardware and mount it according to the manufacturer's instructions.