8. It is a mitzvah to place the Chanukah candles between three and ten
handbreadths ("tefachim"(1)) above the ground (2). Should one place them
above ten handbreadths (or below three), one has still fulfilled one's
obligation. Nevertheless, if a person places them more than twenty "amos"
("cubits") above the ground (3), he does not fulfill his obligation,
because something placed higher than twenty cubits is not in the normal
range of vision, [and thus, will not be noticed] (4).
When a person lives on the second story of a building, he may place [the
Chanukah lights] in a window even though it is more than ten handbreadths
high (that is, above the apartment floor). If, however, the window is more
than twenty cubits above street level, it will not be noticed by the
passersby in the public thoroughfare. In that case, it is preferable to
light them next to a doorway [within the home].
(1) Opinions among the authorities as to the exact length of a 'tefach'
('handbreadth') range between 8 and 10cm ( 3 to 4 inches).
(2) Anything placed below three handbreadths is considered as if it were on
the ground, and it is thus not obvious that the owner placed it there
intentionally. The reason that it should be placed below ten handbreadths
is that lights used for illumination are usually placed above that height,
and therefore it will be obvious that the menorah has been lit for the
mitzvah of Chanukah (See Mishna Berura 671:27)
(3) Opinions among the authorities as to the exact length of an "Amah"
("cubit") range between 48 and 60cm (20 to 24 inches).
(4) And hence, the candles would not serve to publicize the miracle, which
is the main purpose of the mitzvah.