In a large number of paintings and drawings Johns deploys or depicts a mechanical device: the compass arm that he uses to scrape paint. The scrape is yet another mechanical procedure for applying or, in most cases, smearing and removing, passages of paint and other media. The device is a slat of wood, sometimes a stretcher bar or a ruler. Both the instrument and its scrape remind us that a painting is not just an image but, perhaps primarily, an object: canvas tacked to a constructed stretcher, applied with pigment, and moved around the studio like a piece of furniture; something that does not just represent the world but exists in the world as an entity in its own right; something that, as the ruler implies, can be measured for actual size. In interviews throughout the period Johns was at pains to address the painting as almost a utilitarian object . "A painting," he said, "should be looked at the same way we look at a radiator."
Johns introduced the mechanical device in 1959, in the painting Device Circle. The wooden slat is attached at one end to the center of the canvas, from which it pivots to incise a circle in the paint surface. This is the kind of tool Johns used to plot or delineate the perfect circles of the target’s bands; now the tool itself and its abstract application have been substituted for the target image. Device Circle also introduced another change in Johns’ technique: the use of long brushstrokes and an even distribution of red, yellow, and blue, among other colors, across the canvas.