How to Rack a Prefab Fence
Wooden fences are often created from prefabricated sections mounted to posts. The prefabricated fence sections can either be purchased from a supplier, or built on site. Racking is the process by which a prefabricated panel is squared, meaning that each corner is a perfect 90-degree angle. On large structures such as a fence panel, special care is needed to keep the structure square rather than a parallelogram.
Hammer a nail into the top left corner of the fence panel, ideally in the vertical structural member of the fence. The nail should be 1 inch from the top and left edge of the fence. Leave about 1 inch of the nail exposed.
Measure 3 feet from the nail along the vertical structural member, and mark the spot with a pencil point. This point should also be 1 inch from the left edge of the fence panel.
Place a second nail at the spot you just marked, again leaving about an inch exposed. This will be nail No. 1.
Measure 4 feet along the horizontal structural member at the top of the fence panel, and one inch from the top edge of the fence panel. Mark the spot and place another nail, which will be nail No. 2.
Tie one end of a piece of string to nail No. 2. Make a mark on the string exactly 5 feet from this nail.
Pull the string from nail No. 2 to nail No. 3. Adjust the fence until the 5-foot mark on the string is exactly lined up with nail No. 3. The fence panel is now racked, and all corners should be 90-degree angles.
Secure the fence section in place with a stringer—a single piece of wood running between two diagonal corners. Secure the stringer with screws, and leave in place until the fence panel is installed and secured to the fence posts.
Remove the stringer and the nails after installation is complete.
Things You Will Need
- 3 nails, any size
- Tape measure
- Length of board, any width, long enough to go from corner-to-corner of the fence panel
- Screw driver or driver-drill
- The 3:4:5 relationship is a set of Pythagorean numbers, and define a right triangle. You can also use any multiple, such as 6:8:10, and larger multiples will give more accurate results.
- For large fence panels, a second diagonal stringer may be needed to keep the panel racked until installation is completed.
- It is tempting to use a large framing square to rack fence panels, but the results are usually unsatisfactory.