Abstract: A friction stay has a base member for connection to a fixed window frame. A linkage is provided and mounted on the base member and including an arm which connects to an opening window leaf. The linkage includes a part pivotally mounted on a slider carried by the base member for sliding movement as the arm moves between closed and open positions. A locking member is carried on the slider or on the arm and, as the window leaf is moved to the closed position, the locking member is moved to a position in which it projects from the base member and engages with a window frame to prevent unauthorized separation of the base member from the frame. The locking member may be carried by the slider or by the arm.