According to the report "Defensive Earthworks at Becan, Campeche, Mexico, Implications for Maya Warfare" by David L. Webster: "A series of low mounds . . . 1-3m high, lines the inner bank of the moat (ditch); in some places these are clearly seen to be the remains of structures." . . . "I suspect that a (wooden) palisade may well have existed but that all traces of it have been obliterated. About the only remaining evidence would be a line of post holes or soil discolorations along the outer edge of the embankment, but this is precisely where the most severe erosion has taken place." . . . "Defenders, possibly screened by a palisade, could have rained long-distance missiles on approaching enemies using spear throwers and slings. The cleared ground on the outside of the ditch would have left attackers with little protection, and their approach would have been easily spotted by observers on tall buildings (towers) such as Structure I, who could have directed reinforcements to threatened points." [Michael and June Hobby, Proofs of the Book of Mormon, p. 43]
Alma 50:4 He caused [towers] to be erected that overlooked those works of pickets . . .: Moroni had them dig deep ditches around their cities with heaps of earth topped by strong timbers and sharp pickets, and with towers from which they could cast stones. [W. Cleon Skousen, Treasures from the Book of Mormon, Vol. 3, p. 3130] [See also the illustrations for Alma 49:2]