Appearance: Ancient Egyptians wishing to travel up the Nile river had only to take advantage of the force of the prevailing winds that blew south. In art, river boats are typically shown under sail. The hieroglyph for sail was a determinative not only for words such as "sail" and "ship's captain", but for such words relating to the wind, and by association the concept of "breath".
Meaning: In the Book of the Dead, the deceased were often shown holding an unfurled sail as an illustration for Spell 38A: "Living by Air in the Realm of the Dead." The sail represents the breath of life which would be availible to the deceased in the afterlife. Many times, the dead are shown holding a sail and the ankh ("life") which illustrated the idea of "the breath of life."
The hieroglyphic sail was also seen in many Book of the Dead illustrations in which the deceased must cross the celestial river in a boat. This river was often associated by the ancient Egyptians with the Milky Way. The boat the deceased used was powered on its journey by the sail which, once again, carries the connotation a breath and life in the afterlife.