The Hammer Strength Vertical Knee Raise, or VKR, also known as a power tower or knee raise station, is a piece of free weight exercise equipment that works to build abdominal and core strength. It usually has a backrest and fore-arm rests, with vertical handles at the ends of the arm rests, and often includes parallel horizontal handles for performing dips, and/or a pull-up bar attached to the top. Also comes with attached Ab Bench.