Abstract: The disclosure relates to a secure locking mechanism for a sliding door or window. It comprises a toggling pair of bars, one of which is attached to the door frame and the other to the casing so that the bar lies across the fixed pane. The first bar is an inverted channel which encloses a portion of a second preferably solid bar. A pair of longitudinally side by side holes is drilled through both bars in the overlapping portion. The bars are joined in this area by one or more pins inserted through the holes. One hole is located adjacent to the distal end of the solid bar so that it can act as a pivot when the bars are united by a pin passing through this hole. The bars can then toggle to permit the door to be opened. If both holes are pinned or if a single pin is placed so that it passes through the other hole in the solid bar the assembly is securely locked.