1,741. When One is on the Roof and the Other is Below
Hilchos Geirushin 5:3
Let’s say that a woman is standing on her roof and her husband is standing in his courtyard below and he throws a get up to her. Divorce is effected once the get reaches the airspace of her roof’s guardrail or within three handbreadths of the roof (about nine inches), assuming that the get then lands on her roof. If the get is erased or destroyed by fire before reaching the woman, divorce is not effected. This is so even if the get is erased or destroyed after entering the airspace of the woman’s property or within three handbreadths of her roof. Since the get will never land, it is invalid.
Hilchos Geirushin 5:4
If the man stands on his roof and his wife stands in her courtyard below and he throws her a get, then divorce is effected once the get leaves the airspace of his property and enters the airspace of her property.