tiě chǔ chéng zhēn
see 磨杵成針|磨杵成针[mo2 chu3 cheng2 zhen1]
铁
tiě
iron (metal)
杵
chǔ
pestle
成
chéng
short name for Chengdu 成都[Cheng2 du1]
针
zhēn
variant of 針|针[zhen1], needle
