A cylinder hone is an abrasive tool used to prep cylinder walls for new piston rings. It comes in two styles: a three-stone hone with flat spring-loaded stones, or a flex-hone (dingleberry hone) with abrasive balls on wire stems. The tool attaches to a hand drill. As it spins and moves up and down the bore, it scrapes away glaze and creates a fine crosshatch pattern. This pattern of tiny scratches holds oil to lubricate the rings during engine break-in.
Cleaning the cylinders after honing is critical. The stones leave behind abrasive grit that will destroy new bearings. Do not use solvent or gasoline to clean the bores, as it will wash the grit deeper into the metal pores. Scrub the cylinder walls with hot, soapy water and a stiff brush, then dry them and wipe them down with clean engine oil until a white paper towel shows no grey residue.