9. The Chanukah candles should be in a single row of equal height; one
should not be lower or higher than another. There should be a space
between the candles (1) so that the flame of one does not approach the
other thereby giving the appearance of a torch ("medurah") (2). When using
beeswax candles, they should also be separated so that they will not cause
each other to heat up, melt, and thus become ruined.
[The following rules apply] should one fill a dish with oil and place wicks
around it: If one covers the wicks with a [perforated] cover (that is, a
cover which has a separate hole for each wick), each wick is considered to
be a single candle (3). If one does not place a [perforated] cover over
them, [the wicks in the bowl] are not even considered to be a single light
(4), because they resemble a torch. A lamp that has two or more openings
should not be used by two people, even on the first night, because it is
not obvious how many candles [each person] is lighting (5).
(1) The space should be at least the width of a thumb. Opinions as to the
exact width range from 2.24 cm (.885 inches) to 2.48cm (.98 inches).
(2) A "medurah" consists of two or more combined flames, and is invalid for
the mitzvah of Chanukah.
(3) Although they are drawing from the same fuel source, since the wicks
appear separate, they are considered separate candles in terms of the
mitzvah of Chanukah. This is true only when the cover was in place before
the wicks were lit, however, if they were lit first and then covered, they
must be extinguished, covered and then relit (Mishna Berura 671:13).
(4) That is, one cannot fulfill one's obligation with it even on the first
night, when only one candle is lit.
(5) This is true when there is only room for two lights on the menorah.
However, since our menorahs have room for eight lights, it can be used
simultaneously by two people, each lighting at opposite ends (Ibid. 671:12).