Got to agree with Robin on this one. When we played it at school the Knurr was the ball (seem to remember golf balls being used) and the spell launched it. Our where a simple cup on a stick affair -- like a spoon real, with a another underneath by the "cup" end. Then you stamped on the handle end to launchthe knurr.
The bit you hit hte knurr wit hwas just called a bat.
The bit you hit hte knurr wit hwas just called a bat.