An accessory (52, 62, 62A, 63B, 72, 82, 92, 112, 112A) configured for repositionable attachment to a channel element (30, 160, 160A) that includes a rear wall (32, 162), a shelf (36, 166) extending forward from the rear wall (32, 162), a lower lip (37, 167) extending generally downward from a leading edge of the shelf (36, 166), and a plurality of accessory motion restraints (174, 188) which are laterally spaced in relation to one another and located above the shelf (36, 166), the accessory comprising: an accessory body (60, 130) configured to be received by the channel element (30, 160, 160A), wherein the accessory body (60, 130) comprises multiple laterally spaced restraint cooperating elements (111, 138, 184) and a pivotally mounted spring-biased clasp that is configured to pivot relative to the accessory body (60, 130) and that includes a hook element configured to engage the lower lip (37, 167) when the accessory body (60, 130) is received by the channel element (30, 160, 160A); wherein the multiple laterally spaced restraint cooperating elements (111, 138, 184) are configured to cooperate with multiple accessory motion restraints (174, 188) of the plurality of accessory motion restraints (174, 188) to inhibit lateral movement and rotation of the accessory body (60, 130) relative to the channel element (30, 160, 160A) when the accessory body (60, 130) is received by the channel element (30, 160, 160A); and wherein the accessory (52, 62, 62A, 63B, 72, 82, 92, 112, 112A) comprises one of the following features (a) or (b): (a) the multiple laterally spaced restraint cooperating elements comprise multiple laterally spaced protrusions (111, 138) extending from a surface of the accessory body (60, 130) and arranged to be received by the plurality of accessory motion restraints (174, 188) that are embodied in a plurality of apertures or recesses defined in the channel element (30, 60), with the multiple laterally spaced protrusions arranged to be received in multiple apertures or recesses (174, 188) of the plurality of apertures or recesses (174, 188); or (b) the multiple laterally spaced restraint cooperating elements (111, 138, 184) comprise multiple apertures or recesses defined in the accessory body and arranged to receive the plurality of accessory motion restrains (174, 188) that are embodied in a plurality of protrusions extending from a surface of the channel element, with the multiple apertures or recesses (1840 arranged to be received in multiple protrusions of the plurality of protrusions. an accessory body (60, 130) configured to be received by the channel element (30, 160, 160A), wherein the accessory body (60, 130) comprises multiple laterally spaced restraint cooperating elements (111, 138, 184) and a pivotally mounted spring-biased clasp that is configured to pivot relative to the accessory body (60, 130) and that includes a hook element configured to engage the lower lip (37, 167) when the accessory body (60, 130) is received by the channel element (30, 160, 160A); wherein the multiple laterally spaced restraint cooperating elements (111, 138, 184) are configured to cooperate with multiple accessory motion restraints (174, 188) of the plurality of accessory motion restraints (174, 188) to inhibit lateral movement and rotation of the accessory body (60, 130) relative to the channel element (30, 160, 160A) when the accessory body (60, 130) is received by the channel element (30, 160, 160A); and wherein the accessory (52, 62, 62A, 63B, 72, 82, 92, 112, 112A) comprises one of the following features (a) or (b): (a) the multiple laterally spaced restraint cooperating elements comprise multiple laterally spaced protrusions (111, 138) extending from a surface of the accessory body (60, 130) and arranged to be received by the plurality of accessory motion restraints (174, 188) that are embodied in a plurality of apertures or recesses defined in the channel element (30, 60), with the multiple laterally spaced protrusions arranged to be received in multiple apertures or recesses (174, 188) of the plurality of apertures or recesses (174, 188); or (b) the multiple laterally spaced restraint cooperating elements (111, 138, 184) comprise multiple apertures or recesses defined in the accessory body and arranged to receive the plurality of accessory motion restrains (174, 188) that are embodied in a plurality of protrusions extending from a surface of the channel element, with the multiple apertures or recesses (1840 arranged to be received in multiple protrusions of the plurality of protrusions. (a) the multiple laterally spaced restraint cooperating elements comprise multiple laterally spaced protrusions (111, 138) extending from a surface of the accessory body (60, 130) and arranged to be received by the plurality of accessory motion restraints (174, 188) that are embodied in a plurality of apertures or recesses defined in the channel element (30, 60), with the multiple laterally spaced protrusions arranged to be received in multiple apertures or recesses (174, 188) of the plurality of apertures or recesses (174, 188); or (b) the multiple laterally spaced restraint cooperating elements (111, 138, 184) comprise multiple apertures or recesses defined in the accessory body and arranged to receive the plurality of accessory motion restrains (174, 188) that are embodied in a plurality of protrusions extending from a surface of the channel element, with the multiple apertures or recesses (1840 arranged to be received in multiple protrusions of the plurality of protrusions.