Jeff Nelson, age 12, of Richmond, Va., for his question:

WHAT IS A WHETSTONE?

A whetstone can be any abrasive stone, either natural or artificial, that is used for grinding and sharpening knives and metal tools that require sharp edges.

Artificial abrasives are often used. Included is silicon carbide as well as aluminum oxide.

Usually the whetstone used for giving an extra sharp finish to the blade of a knife is a block made from a fine¬grained variety of quartz. Called novaculite, the stone is selected because it can withstand a great deal of wear and produces sharp edges on knives quickly.

Friction is the element at work to provide a sharp edge when metal is carefully stroked against, the stone.