noun
scrawl; stiff, angular handwriting
Refers to handwriting that is stiff, angular, and hard to read, likened to bent nails. Often used self-deprecatingly or to criticize poor penmanship.
彼の字はまるで金釘流だ。
His handwriting is just like a scrawl.
金釘流で書かれたメモを解読するのに苦
I struggled to decipher the note written in that stiff, angular handwriting.
達筆 means skillful or beautiful handwriting, the opposite of 金釘流.
Compound of 金 (metal), 釘 (nail), and 流 (style). The term likens stiff, angular handwriting to bent metal nails.