rubstone
Also found in: Wikipedia.
rubstone
(ˈrʌbˌstəʊn)n
(Tools) a stone used for sharpening or smoothing, esp a whetstone
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014