Security device for sliding door or sliding window assembly

A security device can be provided to selectively restrict or prevent the opening of a sliding door, sliding window, or other sliding panel or other closure. For example, the security device can include a base plate that selectively engages a barricade member (or lock rail). While the barricade member is engaged with the base plate (in a locked state), the barricade member and base plate cooperate to restrict or prevent the sliding door, window, panel or other closure from moving to an open position (or moving out of a closed position). The barricade member can be moved relative to the base plate (to an unlocked state) to allow unrestricted movement of the sliding door, window, panel or other closure. The security device can include stop members that may restrict or prevent complete removal of the barricade member from the base plate.