Abstract: The invention comprises an apparatus for arm exercise for therapy of a subject. The apparatus comprises a base comprising a planar upper surface. A first set of parallel rails are affixed to said upper surface of the base, the first set of parallel rails comprising a first rail and a second rail positioned parallel to each other and separated from each other by a predefined first distance. A second set of rails comprising at least a third rail having a first end and a second end are also provided, wherein said first end is slidably mounted on the first rail and said second end is slidably mounted on said second end. A sliding mount is slidably affixed to the second set of rails, and configured such that said sliding mount can be slidingly moved between the first end and the second end of the third rail.