How to Make a Sag-Proof Wooden Gate

Build as many diagonal braces into the gate as possible. Sag occurs when a shape with four or more sides succumbs to gravity. Triangles are strong because they can't change their shape. When you include a diagonal brace on a gate, you create triangles, which strengthen the gate's structure.

Measure the diagonal distance from the top corner of the hinged side of the gate to the bottom corner of the opposite side. Cut a 2-by-4 to this length.

Screw the 2-by-4 onto the gate with 3-inch-long screws. Put screws in at the corners and at any other parts of the gate that the 2-by-4 crosses. Be sure to put the upper corner on the side with the hinges.

Alternatively, you can install a cable fitted with a cable tensioner instead of a 2-by-4 to allow you to tighten the gate over time. A cable that extends from the upper corner of the hinge side to the lower corner of the opposite side helps support the entire gate. If the gate begins to sag, tighten the cable tensioner to bring it back up.

Support the swinging side of the gate by installing a wheel underneath the corner. Secure the wheel by bolting its plate to the bottom face of the gate. This technique only works well if the gate opens onto a very flat or paved road. If the swing area of the gate is uneven or rocky, a wheel will cause more problems than it solves.