Compiled Laws, Chapter 168. Michigan Election Law § 168.501

Sec. 501.  The master registration cards must be filed alphabetically and must be termed the “master file”.  The master file must contain the signature of each elector registered in the city or township, unless the clerk of the jurisdiction has access to the qualified voter file and the elector has a digitized signature in the qualified voter file.  If an elector is unable to write, or sign his or her name because of a physical disability, the master file must contain the mark or signature stamp used by that elector when a signature is required.