on each night of hanukkah, a new branch is lit. the ninth holder, called the "shamash" ("helper" or "servant"), is for a candle used to light all other candles or to be used as an extra light. to be kosher, the shamash must be offset on a higher or lower plane than the main eight candles or oil lamps, but there are differing opinions as to whether all the lights must be arranged in a straight line, or if the channukiah can be arranged in a curve.