** How to build it**
**( 1 ) **Get three 16-foot lengths of a cast-off telephone pole (your local phone company will sometimes sell them). Or, use 16-foot 6x6-inch or 8x8-inch pressure-treated beams from the lumberyard. Sink two vertical sections 31/2 feet deep in the ground. If you can't dig down that far, seat the uprights as deep as you can, then shore them up with 6x6-inch angle braces.