A frameless display is a display with no perceptible boundaries; it appears to be embodied in the physical world. Frameless displays are created by projecting visual elements on a black background into a physical environment. By considering visual arts and design theory together with our own experience building about a dozen applications, we argue the importance of this technique in creating ubiquitous computer applications that are truly contextualized in the physical world. Nine different examples using frameless displays are described, providing the background for a systematization of frameless displays pros and cons, together with a basic set of usage guidelines. The paper also discusses the differences and constraints on user interaction with visual elements in a frameless display.