Apply A Protective Covering
Once all this has been done you're now ready to begin applying a protective covering to the checkering. This covering will be composed of plain old masking tape. I normally use tape that is about one-inch wide. You can use wider tape, but I've found that the narrower tape is easier to use on the curved surfaces of a stock and it tends to lay flatter with less effort.

A plastic picnic knife with the serrations removed is used to press the tape down into the borderlines of the checkering panel.

Tear off strips of tape that are about an inch longer than the length of the checkering panel. No need to be particularly precise as long as the tape extends beyond the borders of the panel when it is applied. Place the strip of tape over one edge of the panel. Now with additional strips of tape, overlap the first tape strip and gradually cover the entire checkering panel. Don't worry about the ends of the tape not matching the outline of the panel. Use the body of a pencil or pen to smooth the tape over the panel. You should be able to see traces of some lines of the checkering as well as the borderlines around the panel that you earlier deepened.

Take an ordinary plastic picnic knife and file any serrations or teeth off the blade. You want the end of the rounded blade to have a nice sharp edge. Once the knife has been prepared, use it to go over those borderlines around the checkering panel. Use the knife to depress the tape into the borderlines. Don't try to cut the tape, just depress it.

Using a regular hobby-type razor knife, trace over the depressed borderlines that have been outlined in the tape. Don't try to cut into the wood. Use just enough pressure on the razor knife to cut the tape. Once the tape has been cut, pull away any tape that extends outside the checkering panel. If you have done a good job with the razor knife, the tape should come off with little or no resistance. You should end up with a perfect outline of the checkering covered by the tape that remains on the stock.

Leave The Covering In Place
You can now move forward with sanding and refinishing your stock with little or no danger of damaging the checkering. Of course, you still have to be reasonably careful around the checkering, but the masking tape cover will go a long way towards protecting it.

The protective cover for the checkering should remain in place even when the finish is applied. Don't worry about getting finish on the tape. In fact, most finishes will just make the tape stronger and a better protective covering. Using whatever method and materials you choose, finish the stock. It doesn't matter whether you are applying an oil finish or polyurethane; leave the tape covering in place until you have achieved the final finish you want. This includes any rubbing out of the finish with pumice or other stock-rubbing compounds.