Abstract: This invention relates to universal connecting elements for removably joining together frame members such as posts, braces, stays or the like. The same connecting element is used at all corners and/or main points of the frame structure, and consists of two open-ended sleeves oriented at 120.degree. to one another, and a third sleeve open at both ends thereof which extends in one direction only from a plane defined by the forwardmost faces of the two sleeves, the third sleeve being oriented at 90.degree. to said plane.