What calligraphy does the iron hook and silver pen refer to?

——? Ou Yangxun's On Pen: Wandering and pitching, glory and romance are just iron paintings, charming as silver hooks. ] describe brush strokes as stiff as flies and as gentle as silver. -iron hooks and silver strokes are not idioms. 【 Zhang Cuishan's heart moved: "Master left a funeral note in the air." His nickname is' iron hook and silver pen', because his left hand uses a rotten silver tiger head hook and his right hand uses a wrought iron judge pen. ]?