A system for use in securing bits against rotation in a motor grader may include a bit, with the bit having a shank. The shank may include a locking portion. The system may include an adapter board including a hole configured to receive the shank of the bit. The system may also include an anti-rotation plate configured to engage the locking portion of the shank of the bit such that the anti-rotation plate constrains the bit against rotation with respect to the adapter board.