17 The honing work is complete, and the engine is on its way to be decked. But Troutman offers one last tip: Notice the vertical line down the cylinder wall? That’s a mark left by the dial bore gauge. There’s no damage to the bore, but if you don’t see this line it usually means the machinist didn’t do a final check after his last honing pass. Also, the machinist should check the bottom and top of every cylinder, so that line should extend all the way to the bottom of the cylinder bore. That witness line can sometimes be wiped off if you put some elbow grease to it, so it isn’t a foolproof method of checking behind your machinist—but if you don’t see them, it’s worth asking.