A knife, comprising: a body having a first end, a second end, and an opening at the first end; a slide member constructed and arranged to be slideable in the body, the slide member arranged to engage a blade assembly that comprises a plurality of releasably attached blade members that can be separated from one another, the blade assembly comprising an engagement opening, and wherein the slide member includes an engagement structure that is arranged to engage the engagement opening so that the blade assembly moves with the slide member, the slide member being movable to position the blade assembly at a position of use wherein at least one of the blade members has at least a portion thereof that projects from the opening at the first end, and to position the blade assembly at a release position wherein the blade assembly can be released from the slide member when at the release position, the slide member also movable to retract the blade assembly into the body towards the second end to a retracted position; and an actuator member constructed and arranged to be actuated to thereby move the slide member to a disengaged configuration wherein the blade assembly can be disengaged from the slide member to permit the release therefrom, the actuator member comprising a rotatable lock portion that is rotatable between a locked position and an unlocked position, and wherein in the unlocked position, the lock portion permits the sliding member to slide along the body; wherein the positioning of the blade assembly at the release position and subsequent movement of the slide member to the disengaged configuration by actuation of the actuator member releases the blade assembly from the slide member; characterized in that: in the locked position, the rotatable lock portion engages a receiving portion of the body of the knife so as to create a clamping force thereon to prevent the sliding member from sliding along the body; and when the blade assembly is at the release position and the rotatable lock portion is in the unlocked position, the actuator member is configured to be pressed inwards towards the receiving portion and thereby disengage the blade assembly from the slide member. a body having a first end, a second end, and an opening at the first end; a slide member constructed and arranged to be slideable in the body, the slide member arranged to engage a blade assembly that comprises a plurality of releasably attached blade members that can be separated from one another, the blade assembly comprising an engagement opening, and wherein the slide member includes an engagement structure that is arranged to engage the engagement opening so that the blade assembly moves with the slide member, the slide member being movable to position the blade assembly at a position of use wherein at least one of the blade members has at least a portion thereof that projects from the opening at the first end, and to position the blade assembly at a release position wherein the blade assembly can be released from the slide member when at the release position, the slide member also movable to retract the blade assembly into the body towards the second end to a retracted position; and an actuator member constructed and arranged to be actuated to thereby move the slide member to a disengaged configuration wherein the blade assembly can be disengaged from the slide member to permit the release therefrom, the actuator member comprising a rotatable lock portion that is rotatable between a locked position and an unlocked position, and wherein in the unlocked position, the lock portion permits the sliding member to slide along the body; wherein the positioning of the blade assembly at the release position and subsequent movement of the slide member to the disengaged configuration by actuation of the actuator member releases the blade assembly from the slide member; characterized in that: in the locked position, the rotatable lock portion engages a receiving portion of the body of the knife so as to create a clamping force thereon to prevent the sliding member from sliding along the body; and when the blade assembly is at the release position and the rotatable lock portion is in the unlocked position, the actuator member is configured to be pressed inwards towards the receiving portion and thereby disengage the blade assembly from the slide member. in the locked position, the rotatable lock portion engages a receiving portion of the body of the knife so as to create a clamping force thereon to prevent the sliding member from sliding along the body; and when the blade assembly is at the release position and the rotatable lock portion is in the unlocked position, the actuator member is configured to be pressed inwards towards the receiving portion and thereby disengage the blade assembly from the slide member.