A Gripper

1. A person or thing that grips something.
2. A cover on the handle of a bicycle, tool, etc, that makes it easier to grip.
3. (curling) A rubber or other material attached to a curling shoe to improve traction on the ice.
4. (rail transport, slang) A ticket collector.
5. (computing, graphical user interface) A visual component on a window etc. enabling it to be resized and/or moved