sweepboard
/ˈswiːpboʊrd/Definitions
1. noun
A flat piece of wood or plastic that is attached to a skateboard, used for balance and support
“She used a sweepboard to learn how to balance on her skateboard.”
2. noun
A flat piece of wood or plastic used in various applications such as a base or support
“The carpenter used a sweepboard to provide support for the heavy load.”