Abstract: A retractable utility knife comprises a handle having a front portion and a rear portion, a blade carrier slideably mounted in a passageway in the front portion of the handle for positioning a blade in retracted-protected, exposed-cutting, or advanced attachment-detachment positions, with the passageway extending to the front portion of the handle a sufficient distance to position a forward mounting lance of the blade carrier outside the handle to free the blade for detachment from the mounting lance by grasping the front portion of the blade and lifting it off the carrier.

Abstract: A safety cap assembly for a craft knife having a blade and a handle that comprises a cap housing having a front end portion and a rear end portion with an opening at the end of the front end portion for receiving the knife blade, an attaching member located on the front end portion of the housing for attaching it to the knife handle, a sleeve mounted on the housing adapted for sliding back and forth between the front end and the rear end portions of the housing for closing the attaching member in attaching position when the sleeve is at the front end portion of the housing and for opening the attaching member when the sleeve is at the rear end portion, stop members at the ends of the housing for preventing the sleeve from slipping off the housing, and a safety-locking member on the housing for releaseably locking the sleeve in position on the front end portion when the sleeve is closing the attaching member whereby to prevent the cap assembly from opening and being pulled off the knife accidentally.