In 2010 galleries in Berlin and Paris decided to swap venues, and Henriksen, with his gallery Sommer & Kohl, proposed an exchange with Denise René, a gallery founded by a legendary figure in art history who put on her first exhibitions shortly after the end of World War II. Once the girlfriend of Victor Vasarely, she helped define modernism in Europe, and was the first to organise a solo show of Piet Mondrian’s work. When Henriksen visited the space to discuss curating a show there, his attention was drawn to the door handle, which is square on one side and round on the other. His questions about the history of the door handle could only be answered by the nearly hundred-year-old René herself, who explained that it had been designed by Vasarely. Henriksen’s exhibition ‘Circles, Squares, and a Door Handle’ alluded to this door handle as well as a magazine from the milieu of the gallery’s artists titled Cercle et Carré(Circle and Square). The show included work by Max Bill – a ball that has spread out to be a square – along with pieces by Sonia Delaunay, Hans Arp, Vasarely, and Jean Tinguely. Henriksen’s own contributions included a composition made from two plaster boards cut into circles, titled Plaster, 2010. Plaster, Henriksen points out, refers to a material but also means to spread things out. This show was a follow-up to a 2008 exhibition in the Galleri Würth outside Oslo, where Henriksen’s work was shown alongside pieces by Hans Arp from the Würth Collection.