A side rail for a cargo bed of a vehicle enables the fitting or mounting of a broad range of automotive accessories to a roll top cover. The side rail comprises: an elongate body that defines a longitudinal axis; an axially extending drive channel disposed at a medial side of the body and defining an opening therein for receiving a drive chain, the drive channel having a recessed inner portion and a stepped outer portion adjacent the opening; an axially extending first support channel recessed in an upper side of the body and opening upwardly therefrom; and an axially extending second support channel recessed in the upper side of the body and opening upwardly therefrom, the second support channel disposed laterally adjacent to the first support channel.