In Chicago, the maximum legal blade length for carrying a knife on public property is 2.5 inches, whether openly or concealed. This restriction applies to all knives, including folding and fixed-blade knives, and is stricter than the state of Illinois' general 3-inch limit for public carry. The city's ordinance also prohibits certain types of knives, such as knuckle knives, ballistic knives, and automatic knives, unless the individual possesses a valid FOID card. This 2.5-inch rule is enforced under the Chicago Municipal Code and has led to the production of "Chicago edition" knives designed to comply with the local law.