Knife Edge Two Piece 1962-65, shows Moore’s re-engagement with abstraction during the 1960s. The work comprises two upright forms, set parallel to each other on a bronze base. As you move around the sculpture, the view changes dramatically. From the longest edge, the viewer is confronted by wide, flat masses. End-on, the thinness of the two elements is revealed, the flat masses now reduced to narrow forms with razor-sharp edges which stretch upwards, slicing through the sky.

The original inspiration for Knife Edge Two Piece came from a fragment of bone. Moore admired the structural and sculptural properties of bones, their combination of lightness and strength, and referred to the breast bones of birds in particular as having the ‘lightweight fineness of a knife-blade.’[1] Translated into a monumental scale, the forms also recall the rock formations that Moore admired as a child. The two forms are like the walls of great canyons, while the slither of negative space between them forms a fissure in the rock.

Moore saw the relationship between the two forms in Knife Edge Two Piece as different to his other two piece sculptures. Describing the working model, he explained: ‘In some of the other works the relationship is of one form accommodating another form, that is, one fitting into the other; in others the contact is that of points nearly connecting, but in [this] sculpture it is a kind of sliding relationship, like two sliding doors.’[2] Indeed, as one moves around the work, the space between the forms seems to open and close, revealing and then concealing the view beyond.

All three casts of Knife Edge Two Piece are on public display. One occupies a prominent position outside the Houses of Parliament in Westminster. The other two are in Queen Elizabeth Park, Vancouver, and the Kykuit Rockefeller Estate, New York. Moore donated the Westminster cast to the nation through the Contemporary Art Society, and chose the site himself. Unveiled in November 1967, the siting was not universally popular, with one MP asking Parliament why ‘this lovely part of Westminster should be littered with something that looks like a crashed unidentified flying object.’ Since its installation, however, the work has become a familiar backdrop to numerous television interviews, and in 2016 it was granted Grade II* listed status on account of its aesthetic quality, historic interest and for its place in an area historically associated with the display of public sculpture.

Moore later made a larger but reversed version, Mirror Knife Edge 1977 (LH 714), for the entrance to the new east wing of the National Gallery of Art in Washington D.C., designed by the architect I.M. Pei.