A clip for assembling corners of hollow members such as the rails and stiles of an extruded aluminum door. The clip has a double L shape. A portion of the clip inserts into the hollow of a first member and is attached thereto. Another U-shaped portion defining the bottom of the double L extends into the other hollow member for attachment thereto to form a sturdy joint without welding. The first member may have a slot that receives the clip and the clip may be shaped to conform to the internal surfaces of one or both members. Clips may be used at each corner.