Cork cutter sharpener, we had it on here before. Cork cutters are brass tubes of various sizes, they come in sets with "T" handles and they nest together. The tapered end of the tool fits inside the cork cutter and you lightly press the steel blade against the outside of the cutter and rotate the cutter/blade around the cutting end of the cutter to sharpen it. They are often found without the set of cutters and come up for sale as whatsits.