1. Bulldoze a circular pad, a bit more than 51 feet in diameter, to the depth of about a foot. Compact the soil; add 6 inches of graduated stone; and compact, soak, and compact again. Add 4 inches of stone dust; compact, soak, and compact again.
2. Enclose your 51-foot circular area with 10-foot round pressure-treated construction posts set 4 feet apart, leaving an 8-foot opening for entry to the round pen. Set posts 3 feet in the ground, securing them with one sack of Redi-crete each if your soil is sandy or unstable. (Our soil was compacted and strong enough to hold the posts without concrete.)
3. Soak approximately 150 3/4-inch by 6-inch by 16-foot pressure-treated Douglas fir boards until they're soft and pliable. Then make a solid wall by attaching them to the inside of the posts. (We built our wall twelve boards high or 6 feet.) Stagger the boards on the posts to distribute the pressure evenly.
4. Cut the remaining boards to the height of your fence and nail them vertically to the inside to cover the joins at the posts. (Optional finishing touch: Nail a top row of boards horizontally inside the posts.)
5. We built 2 wooden doors in welded metal frames. You could also use all wood, or buy a ready-made metal gate.
This article first appeared in the October 2000 issue of Practical Horseman magazine.