Abstract: An automatic lockable linkage system for use with sliding members, such as a sliding door or window, comprising a first and second telescoping arm member pivotally interconnected adjacent to their inner end portions. Each telescoping arm member also has an outer end which is pivotally connectable to a fixed structure and a sliding member, respectively. When the sliding member is in the closed position, a lockable sliding linkage is automatically positioned over the pivotally interconnected inner end portions of the first and second telescoping arm members retaining the sliding member in the closed position.