The Megillat Esther is a considered a sacred Sefer (Scripture). One of the components of a Sefer is a stick around which the parchment is rolled. While a Sefer Torah requires two sticks, due to its size, the Megillah requires one stick.
There is a disagreement as to where the stick is placed. Some say that it is placed in the beginning of the Megillah, but the Tosafot and Shulhan Aruch (681:2) hold that the stick is attached to the end of the Megillah. Although the Ashkenazim have a custom not to use a stick at all, Maran clearly requires it, based on the Talmud Yerushalmi which compares the Megillah to a Sefer Torah.
One should not read from a Megillah that does not have a stick and should go out of his way to fulfil this Halacha. It is not difficult to attach such as stick before reading from it. Under extenuating circumstances, B'dieved, if the only Megillah available does not have a stick, Hacham Ovadia (Hazon Ovadia p. 143) rules that it may be used and the Berachot may be recited. He writes that in such a case, one may rely on the Rambam who does not mention the stick as one of the critical components of the Megillah. On the other hand, Hacham Bension (Or Lesion Vol. 4, p. 334) disagreed and ruled that the Berachot may not be recited.
SUMMARY
One should make an effort to ensure that the Megillat Esther has a rod around which the parchment is rolled.
