A utility knife has a handle generally defining a handle axis and a remote end provided with an opening. A carriage is slidably mounted within the handle for selective movements through the opening between a retracted position in which the carriage is substantially fully received within the handle and a fully extended position in which the carriage is fully extended through the opening to increase the effective length of said handle by a distance Δl. A blade mounted on the carriage shares the movements of the carriage and has an operative portion that can fully penetrate a work to be cut when the handle axis is inclined at an angle α relative to a surface of the work. A finger of a user most proximate to the work surface is positionable a distance h above the work surface during normal use of the utility knife, Δl and α being selected so that the distance Δl is generally greater that 1.0 inch and the angle α is equal to at least 35°.