A Lansky folding diamond tapered rod (TR600): fine 600 grit, 3.5 in (8.89 cm) diamond rod that folds into a nylon-impregnated plastic handle. Lansky lists uses: regular, serrated, guthook, karambits; also fish hooks and other tools. No lubrication on diamond; clean with water and a lint-free rag, dry before next use. Specs from Lansky's Folding Diamond Tapered Rod page.
Tapered diamond that folds. One serration at a time, or a few strokes on a straight edge.
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