Rib: the power of covering by bowing, as in the tent of a human chest, the roof of a house, or a reef in the sea. Human ribs protect a chest and heart by shedding blows. The roof (ribs) of a house protect it by shedding sun and rain. A reef (rack of ribs) in the sea sheds the sea itself, but catches ships (which are also ribbed.) In each case, it is the bowed form that carries the energy, like a longbow. Unlike such a bow, however, a rib holds the power rather than releases it.
Staghorn Sumac Leaf
All its ribs showing!