Crusoe starts off by constructing a fence at a ten yards in radius from the rock and five feet high out of desire for security from the potential dangers on the island. He then sets up a double tent for storage and simple protection from the element within the fence.
Once the fence and the wall is complete, Crusoe begins carving into the cave to create a cellar so as to separate lodging from storage. This also creates space within the tent for him to put a chair and a table.
Crusoe begins to expand his cave again, desiring more space for storage and a kitchen. However, one day the roof of the cave collapses and from then on, Crusoe begins using posts, like the stakes in the fence, and planks, possibly from the ship, to support the roof the cave as he expands. Crusoe also sets up the posts so that they may partition the rooms.
As he carves further into the cave, he creates pathway from the cave to the exterior of his wall. Presumably, this is done to allow for easier access to the kitchen once he has gathered food since the wall requires a ladder to cross.
Crusoe then begins a series of further expansions to the cave.
After finding the footprint in the sand, Crusoe is alarmed and immediately sets out to fortify the hedge to create a second wall. Earth is removed from the cave and placed against the second wall to make it stronger. Crusoe also creates seven holes and sets up his spare muskets there for further defensive measures. By this time, the trees have also grown bigger to completely hide his fortification from site.