A fastener for plastic bags opened and closed by a slider includes first and second track members with each having one of a pair of interlocking profiles. The fastener has opposite ends with terminations. A slider is mounted on the fastener and has a separation member with a wide portion and a narrow portion positioned in the fastener. The slider, upon complete closure of the fastener, rides up onto a termination moving the wide portion of the separation member out from between the fastener allowing the profiles to lock along the entire length of the fastener.