An artwork gravity knife comprises a first handle body, a second handle body, a knife pushing mount, and a blade box. The first and the second handle bodies are pivoted respectively at the rear end thereof to a pivot such that they can be rotated in relation to each other. The first and the second handle bodies are provided respectively at the front end thereof with a knife pushing mount behind which the blade box is disposed. The blade box also serves to fasten securely the first and the second handle bodies. The blade in use can be replaced easily and safely with those which are kept in the built-in blade box.

A knife comprises a substantially hollow handle, a short knife blade guided longitudinally movable in a knife blade guide track and at least one guided slider member coupled indirectly with the handle side of the longitudinally movable knife blade. The slider member is provided or associated with a longitudinal slot, in some cases penetrating the handle to reach the exterior, and an operating piece. An especially simple replacement of the knife blade is possible since the knife blade is insertable at least indirectly in the knife blade guide track through the longitudinal slot which is designed to meet its spatial requirements. There the knife blade is form-locked and releasably lockable on the slider member which is at least partially removable from the handle.

A utility knife includes a handle having a rod slidably engaged in the front portion. A knife blade is engaged between two boards. A plate is secured to the boards and has a rear portion for engaging with the rod. A spring biases the rod to engage with the plate. The plate may be disengaged from the handle when the rod is moved away from the plate against the spring. The boards are slightly extended outward of the handle for allowing the user to grasp the boards and for disengaging the knife blade from the handle without contacting with the knife blade.

A utility knife employs a slide having a cantilevered lever for capturing a blade therein. A leading blade in a reservoir is capturable by the slide using a tooth resiliently affixed to the slide which is positioned to enter a locking hole in the blade. The tooth may be withdrawn from the hole in the blade whereby the blade may be removed for reversal and reinsertion or for discard. When the captured blade is removed, the slide may be returned to the loading position for capturing the next blade from the reservoir. As long as a captured blade is engaged by the tooth, the slide is prevented from returning to the loading position, and the loading blade in the reservoir is prevented from advancing.

An improved structure art design knife comprised of a front cover, a rear cover, an upper support cushion, a lower support cushion, a blade magazine section, and a blade arrestor section. In addition to providing for convenient blade replacement, the blade magazine section contains a quantity of spare blades to thereby increase art design knife efficiency and, furthermore, enhance the industrial practical value of art design knife structures.