But we can't spend all day making interior decorating plans for the guardroom, so into the SCARP we go! A scarp is the inner side of a defensive ditch, which, in the case of such a fortification as Fort Barrancas, has a firing gallery running along inside with plenty of loopholes for firing rifles at any who are so unwise as to venture within that ditch in an unauthorized fashion. The counterscarp refers to the outer side of that ditch, which in this case is also built to afford defenders plenty of opportunities to shoot at people.