Massachusetts General Laws Part III. Courts, Judicial Officers and Proceedings in Civil Cases (Ch. 211-262) Ch. 217, § 27

An assistant register shall perform his duties under the direction of the register and shall pay over to the register all fees and amounts received as such assistant. He may authenticate papers and perform such other duties as are not performed by the register. In case of the absence, neglect, removal, resignation or death of the register, the assistant may complete and attest any records remaining unfinished and may act as register until a new register is qualified or the disability removed.