A shredder includes a thickness detector device having a contact portion in a throat of a housing. The contact portion is movable by a thickness between opposing major surfaces of at least one article being received by the throat. The thickness detector device includes a detectable portion movable by the contact portion, and a detector for detecting at least one position of the detectable portion that includes a position when the detectable portion has been moved by the contact portion by an amount that correlates to a predetermined maximum thickness. A controller is coupled to the thickness detector, is operable to prevent a motor from driving cutter elements in a shredding direction responsive to the detector detecting that the detectable portion has been moved by the amount that correlates to the predetermined maximum thickness, and is configured to vary the predetermined maximum thickness based on receiving an input parameter.