Compiled Laws, Chapter 168. Michigan Election Law § 168.664

Sec. 664. On the inside of said railing, the said officers shall cause 1 or more booths or temporary rooms to be erected. At least 1 such booth shall be provided at each polling place and not less than 1 for each 100 persons entitled to vote thereat, as shown by the registration book of the precinct. Each such booth shall be built with walls not less than 6 feet high and in such manner that the person preparing his ballot shall be concealed from all other persons. In each booth there shall be provided a shelf of sufficient size with smooth surface on which ballots may be placed to be marked.