Ala. Code § 3-4-1

All inclosures and fences must be made at least five feet high, unless otherwise provided in this chapter. If the fence is made of rails, the rails must be not more than four inches apart from the ground to the height of every two feet. If the fence is made of palings, the palings must be not more than three inches apart. If the fence is made with a ditch, such ditch must be four feet wide at the top and the fence, of whatever material composed, at least five feet high from the bottom of the ditch and three feet high from the top of the bank and so close as to prevent stock of any kind from getting through.