A slider for use with an elongate closure mechanism includes a retention member protruding into a medial space between an upper pair of opposing interlocking members and a lower pair of opposing interlocking members. The retention members define a gap through which the upper pair of opposing interlocking members cannot pass, and that allows the slider to be slidably shifted along the length of the closure mechanism, thereby maintaining the slider operatively disposed thereon. The retention members may have the form of one or more protrusions disposed on an interior surface of a channel sidewall spaced between a top end of the channel sidewall and a bottom end of the channel sidewall.