Abstract: A cornerpiece for multiple pane windows comprises an integrally formed sheet metal piece having orthogonally extending members which are received in the adjacent ends of tubular spacer bars separating the panes of glass in a multiple pane insulating window. The tubular spacer bars form a frame which is interposed between the panes of glass, and the cornerpiece is formed so as to be closely received within the ends of the tubular members, thereby joining adjacent tubular members. The cornerpiece is formed so as to block the ends of the spacer bars to prevent a desiccant that is typically placed in the spacer bars from leaking out of the ends of the spacer bars.