Utility knife

A utility knife comprising:

• a handle comprising a first longitudinal side, a second longitudinal side opposite the first longitudinal side, a top side, a bottom side, and a slot that extends through the bottom side, the slot between the first and second longitudinal sides, wherein the handle comprises a first surface;
• a blade;
• a blade holder, the blade removably coupled to the blade holder, the blade holder pivotable with respect to the handle between an extended position where the blade is exposed and configured to cut a work-piece and a folded position where the blade is within the slot of the handle, the blade holder comprising a first notch and a second notch;
• and
• a spare blade holder comprising a recess that receives a spare blade, the spare blade holder pivotal with respect to the handle between an open position where the spare blade can be removed from the spare blade holder and a closed position where the recess is within the slot of the handle to inhibit removal of the spare blade from the spare blade holder, wherein the spare blade holder comprises a second surface, and wherein the second surface of the spare blade holder engages the first surface of the handle when the spare blade holder is in the closed position to bias the spare blade holder away from the first blade holder;
• a locking mechanism comprising:
• a push button movable between a locked position and an unlocked position, the blade holder pivotable with respect to the handle between the extended and folded positions when the push button is in the unlocked position and the blade holder is held from pivotal movement relative to the handle when the push button is in the locked position, the push button comprising a first portion of a first diameter and a second portion of a second diameter that is larger than the first diameter and a frusto-conical portion between the first and second portions, the second portion of the push button is received in the first notch of the blade holder to hold the blade holder in the extended position and the second portion of the push button is received in the second notch of the blade holder to hold the blade holder in the folded position, and
• a coil spring that biases the push button toward the locked position.