bulwark -
a fencelike structure around a deck (usually plural)
barrier a structure or object that impedes free movement
bulwark -
an embankment built around a space for defensive purposes; "they stormed the ramparts of the city"; "they blew the trumpet and the walls came tumbling down"
embankment a long artificial mound of stone or earth; built to hold back water or to support a road or as protection
fortification,
munition the addition of an ingredient for the purpose of enrichment (as the addition of alcohol to wine or the addition of vitamins to food)
bailey the outer defensive wall that surrounds the outer courtyard of a castle