The fort at Fair Lawn was designed as a redoubt to help control the river traffic on the Cooper River. The tabby fort at Dorchester was also used to control traffic on the Ashley River helping the British to control the two major inland water ways for communication, moving of troops, and commerce. Below is a good example of what the redoubt at Fair Lawn was designed to look like. Notice the earthen walls built up to provide protection, the one entrance, the moat around the entire structure, the one entrance, and other defensive structures.
One key about a redoubt is that is was not meant to house soldiers or their daily chores. The soldiers would of been camped close to the redoubt so they could man it quickly if called for.