Mass. Gen. Laws ch. 54 § 70
No more than four voters, besides election officers and supervisors, custodians of voting machines when acting in the course of their duties, and the city or town clerk, in excess of the number of marking compartments provided, shall be allowed at one time within the guard rail. Where voting machines are used, the number of voters allowed within the guard rail shall not be more than twice the number of voting machines provided. After the time fixed for closing the polls, no voters shall be admitted within the guard rail, except the election officers and supervisors, and except voters who are then in the polling place or in line at the door thereof. The presiding officer of the polling place shall provide or cause to be provided to each voter so outside the guard rail a card or slip bearing such voter's name, and the voter shall as soon as practicable present the same to one of the ballot clerks and shall then be permitted to vote if otherwise qualified. When the polls are closed, the presiding officer shall cause a police officer or other qualified person to be stationed at the end of the line of persons waiting to vote to see that no other persons vote than those who were in the polling place or in line at the door at the time fixed for closing the polls. After the last voter in line at the door has entered within the guard rail, the voters shall be allowed five minutes in which to cast their votes.
Mass. Gen. Laws ch. 54, § 70