Material alteration of negotiable instruments voids the instrument against non-consenting parties and discharges indorser liability. Material alteration of a negotiable instrument renders it void as against any party who was a party at the time of alteration and did not consent, unless the alteration was made to carry out the common intention of the original parties. If an indorsee makes such an alteration, it discharges his indorser from all liability to him in respect of the consideration.