a utility knife is provided which includes a unitary , blade carrier which acts to restrain the blade during heavy use and which prevents the blade from disengaging from the knife . the blade carrier includes a blade support portion , a blade retaining flange for retaining a first edge of the blade , and at least one laterally extending post for receiving a corresponding notch or notches in the blade when the blade is mounted on the blade carrier . the post has a profile which engages the notch in the blade when the blade is subjected to a lateral or twisting force to prevent the blade from disengaging from the blade carrier during use . in this manner , the post on the blade carrier performs the dual function of providing both longitudinal as well as lateral restraint for the blade .