Mass. Gen. Laws ch. 54 § 7A
Any precinct in a town where town meeting members are elected may be divided for the sole purpose of facilitating voting therein. Every such division of a precinct shall be designated by the addition of a letter to the number designating such precinct, or of a number to the letter designating such precinct, as for example, precincts 1A, 1B and so on, or precincts A1, A2 and so on. The number of town meeting members representing such precinct immediately preceding such a division shall remain unchanged and such members shall be elected from the same territory until a general revision of precincts is made. Notice of every such division shall be given forthwith to the state secretary. Except as provided herein, all provisions of law relating to voting precincts and to polling places shall apply to such divisions. Within twenty days after such a division, the selectmen shall cause notice in writing to be given to each registered voter in any precinct so divided specifying the polling place to be used by such voter. A division of a precinct made hereunder shall take effect on the thirty-first day of December following the making thereof.
Mass. Gen. Laws ch. 54, § 7A