Although scrollbar designs differ throughout their history, they usually appear on one or two sides of the viewing area as long rectangular areas containing a bar (or thumb) that can be dragged along a trough (or track) to move the body of the document. This can be placed vertically, horizontally, or both in the window depending on which direction the content extends past its boundaries. Two arrows are often included on either end of the thumb or trough for more precise adjustments. The “thumb” has different names in different environments: on the Mac OS X 10.4 it is called a "scroller"; on the Java platform it is called "thumb" or "knob"; Microsoft's .NET documentation refers to it as "scroll box" or "scroll thumb"; in other environments it is called "elevator", "quint", "puck", "wiper" or "grip"; in certain environments where browsers use agnostic language to the scrollbar terminology, the thumb is referred to as the 'pea' for vertical movement of the bar and still use 'puck' for horizontal movement.