For a sagging gate, first tighten the hinge screws; replace them with longer ones if necessary, or drill through the gatepost and use bolts. Then see if the gate is out of kilter; you may be able to square it with a wire and turn buckle. Finally check the gatepost. If it leans, run a wire and turnbuckle from its top to the bottom of the next post. If that doesn’t work, reset the post. Making a new gate Begin by buying the hardware. The size and design will affect the way you build the gate. Get sturdy, rust-resistant ones; you may need longer screws than are provided. Two hinges are usually enough for a gate 5 feet high and 3 feet wide. Self-closing hinges are a good idea if you have children; loose-pin hinges let you remove the gate easily.
For the width of the gate, measure between the posts, then subtract 1 inch (or more, depending on the design of the hardware). Don’t make the gate too wide. A gate wider than 3 feet is likely to sag; make a pair of smaller gates instead. The height depends on the fence; allow at least 2 inches clearance at the bottom.
Make the frame of 2 x 4s, using lap or mortise-and-tenon joints and waterproof glue. Make sure that the parts are square. Cut a diagonal brace, also of 2 x 4, to fit tightly between the bottom corner on the hinge side and the top corner on the latch side. Attach it with galvanized 10d nails and steel reinforcing plates. Attach siding to match the fence. Then screw or bolt the hinges to the frame.
Prop the gate in place to be sure it fits. If it does, nail the hinges to the gatepost (one 6d nail in each hinge) and swing the gate open to check the clearance. If it is right, remove the nails, and screw or bolt the hinges to the post. Close the gate and position the latch. For a gate stop, nail a strip of 1 x 2 to the latchpost.