Abstract: Four corner pieces are used to connect the ends of two rectangular duct sections together. Each duct wall has a groove at its end and also a flange, the flange in each instance having a resilient rim or lip. The corner pieces comprise two offset legs, the legs each having a web residing in planes parallel to each other and having a connecting portion residing in a plane intermediate said two planes. In this way, one leg is engageable with a portion of a flange on one of the duct sections and the other leg is engageable with a portion of a flange on the other duct section. Due to the resiliency of the flanges, the legs, which have angled flanges thereon, can be snapped into place to retain the two duct sections in a connected end-to-end relationship.