Glue to a throwing bat, or use on top of a table or your lap to smooth the bottoms of your pots with this inexpensive diamond impregnated metal square.  Use water to lubricate surface when grinding. Dry off when finished. 

SELECT 60 Grit, 120 Grit or 180 Grit above.

60 is the roughest, 120 the medium, and 180 the finest

Removing glaze drips

Leveling warped bottoms

Removing wads from wood or soda fired ware

Removing stuck kiln wash from bottom of pot

Making a uneven foot ring flat