PURPOSE: To enable self-aligning plug-in connection and to improve assembly work by providing a truncated cone-shaped peg at one end of an arcuate arm and a tapped hole at the other end of the arcuate arm of a connecting member suitable for use in supporting a horizontal flat element.

CONSTITUTION: The connecting member 101 has an extension arm 102 and a truncated cone-shaped peg 104 is provided at one end 103 of the arm 102. The peg 104 as a male element can be inserted into a truncated cone-shaped recess 223 as a female element. The arm 102 is a bar or rod member, the center line 105 of which circles a quadrant, and the other end 106 opposite to the peg 104 has a tapped hole 107 and an essentially straight cylinder part 110. A pair of the extension arms 202 can be symmetrically joined, and a straight cylinder element 222 can be positioned at the middle region 221 to form another connecting member 201.