Abstract: A sealing device for use in a sealed double glazed window assembly is described and consists of a pair of glass sheets arranged in spaced parallel relationship to form an air space therebetween and of a spacing unit disposed between the inner marginal edges of the glass sheets. The device comprises a flexible plug that fits into holes made in the spacing unit. A blind rivet is used within the plug and consists of a deformed sleeve member and of a ruptured annular member coaxially positioned within the sleeve member. The bottom wall of the plug is made of piercable material so that a piercing member may be introduced in the cavity to penetrate through the bottom wall to thereby have access to the space between the sheets.