A utility knife includes a hollow handle having a slot and an opening at each end. A razor is slidable between each end of the handle and may protrude at each opposing end for cutting use. The razor is mounted to a shuttle which includes a tab that is positioned within the slot. The user may use the tab to slide the shuttle and the blade within the handle between the two ends, as desired. A U-shaped blocking component is pivotally attached to the handle and is used to block sliding movement of the tab beyond a midpoint of the handle to prevent the razor protruding into the user's hand. The user must unlock the blocking element to safely allow the shuttle to be slid past.