His father's kitchen knife. Carbon steel, not stainless, needing the stone every fortnight.
The edge rolls in one place. Four centimetres back from the tip.
He ground it out and the next evening, after cooking, it had rolled again in the same spot. He did it a dozen times. Never more than a millimetre off.
He locked the knife in a drawer and bought a new one from the department store, German, stainless, four hundred and sixty.
The new knife rolled the next day in the same place. He measured it with a caliper: four centimetres from the tip.
He took both knives to the old blade shop in the town. The man there is over eighty. He put his glasses on and turned them over, and over again, and then asked one question: when you cut, how do you hold your left hand?
He showed him — four fingers together, knuckles against the flat of the blade, walking backward.
The old man said: measure it.
He measured from the second knuckle of his left index finger to the web of his thumb.
Four centimetres.