Mass. Gen. Laws ch. 54 § 35
The body, board or official charged with the conduct of elections shall cause to be done all things necessary to properly carry on primaries and elections where voting machines are used. Before every primary and election they shall cause to be placed on public exhibition one or more machines for the instruction of voters. Such machines shall be equipped with ballot labels as nearly as practicable like those to be used on the machine at the primary or election, as to titles of offices, names of candidates and forms of questions. On the day of the election they shall provide at each polling place a mechanical model of the voting machine, which shall be placed outside the guard rail and shall be suitable for the instruction of the voters and illustrating the manner of voting. Before the opening of the polls they shall cause each machine to be prepared for use and delivered at the polling place. On the day of the election the keys to each voting machine shall be delivered by the city or town clerk to the election officers a reasonable time before the opening of the polls in a separate sealed envelope on which shall be written the number and location of the election precinct or polling place, the number of the voting machine, the number of the seal with which it is sealed and the number registered on the protective counter as reported by the city or town clerk. No such envelope shall be opened until at least one of the election officers from each of two political parties are present at the polling place and have examined the envelope to see that it has not been opened. Before opening such an envelope, all election officers present shall examine the seal on the machine to see that it is intact, and they shall compare the numbers on the envelope with the numbers registered on the protective counter and on the seal on the machine to see whether or not they agree. If they do not agree, the machine shall not be opened until the city or town clerk shall have been notified and personally or by the custodian designated under section thirty A shall have examined such machine and certified that it is properly prepared and arranged for the election. If the numbers agree, the election officers shall open the doors of the counter compartment of the machine. All the election officers present shall examine the county compartment of every machine to see whether or not it registers zero. A candidate for public office whose name appears on said machine or his representative duly authorized in writing shall likewise be permitted to examine and check the figures on the back of a voting machine before the polls open to determine that its figures are properly registered. In cities and towns which use printer type voting machines approved pursuant to section thirty-two, such examination by a candidate whose name appears on said machine or his representative, duly authorized in writing, shall be conducted by means of the printer sheets to determine the figures on each machine are properly registered. Polling places shall be open one half hour before voting begins for the purpose of permitting such candidates to examine said machines. After such examination the doors of each counter compartment shall be closed and locked and not again opened until the polls are closed. If any counter shall be found not to be set at zero, the number and letter of such counter, together with the number registered thereon, shall be stated in a writing signed by the election officers and posted on the wall of the polling place, and a duplicate of such writing shall be filed with the election returns. At the close of the polls such number shall be subtracted from the number then found registered on the counter. Each machine shall remain locked and sealed against voting until the time set for opening the polls. It shall be then unlocked for voting and the seal removed.
Mass. Gen. Laws ch. 54, § 35