This paper explores the Boundless Scroll interface that extends the motor space for finger drag motions into the off-screen space using a tracking system around the screen. Seamlessly extended motor spaces enable continuous scroll actions across the on- And off-screens, reducing the chance of clutching and preserving content visibility during longdistance and smooth scrolling actions. We empirically evaluate our new technique, the Boundless Scroll and compare it to ordinary scroll interfaces (Drag and Flick) in two dominant screen devices. The first screen condition uses a large flat touch screen where users manipulate a nonfull- screen window while using the surrounding space as an extended motor space. The second condition is a mobile device to examine mid-air finger scroll motions in the offscreen space using a 3D motion sensor. An empirically controlled study demonstrates our Boundless Scroll's many benefits, such as fewer clutching actions, occlusion-less content observations, and efficient and effortless off-screen acquisitions and also provided further design factors, implementations of the Boundless Scroll, and arounddevice interfaces.