Here's the museum's elaboration on the piece:
When Patsy and Raymond Nasher purchased this work in 1968, it was one of their earliest acquisitions in the realm of modern sculpture. Influenced by the timeless power of Neolithic stone monuments, Hepworth adopted the form of an upright slab. The distinctive hollowed out circles, a device the artist had used in her work as early as the 1930s, open up the solid mass and allow a continuous flow of space through and around the monolith. With the round apertures framing the surrounding landscape and the richly varied green patina of the bronze, the overall effect of the sculpture is one of natural forms and forces.