Abstract: The invention relates to a coupling between two objects via a coupling element. Each object comprises a panel with a continuous hole with four inward protruding tongues which are disposed at 90° to each other and extend over angles of about 22.5°. The coupling element comprises a shank, an insert stop member on both sides so that the coupling element can be inserted in the one or the other direction into the hole, four locking cams on each end zone of the shank which each extend over angles of 22.5° disposed at 0°, (90°?22.5°), 180°, (270°?22.5°), and rotation stop members. The coupling element can be inserted into the hole in a chosen orientation as desired in one of four equidistant angular positions and then rotated through about 22.5° in the one or the other direction, wherein rotation locking means fix the chosen angular position.

Abstract: A modular construction system has at least two profile parts for releasable coupling with a coupling part. The coupling part has on each of at least two sides one or more radially protruding lips. The lips on one side may be rotated to engage a portion of a profile part while the lips on another side may be rotated to engage a portion of another profile part, thereby securing the profile parts to one another.