Abstract: A utility knife for use with a flat blade having a pair of opposite faces has an elongated base part formed with an outwardly directed rear support surface, an outwardly directed front support surface separated longitudinally therefrom, and an inwardly directed intermediate surface between the support surfaces. The blade normally lies on the front support surface and projects longitudinally forward past the base part. An elongated cover part has an inwardly directed rear surface normally riding on the base-part rear support surface, an inwardly directed front surface normally pressing the blade inward against the base-part front support surface, and an outwardly directed intermediate surface. The cover part is displaceable longitudinally between one longitudinal end position with the intermediate surfaces transversely confronting each other and another longitudinal end position with the intermediate surfaces transversely out of alignment with each other.