His hobnailed way of giving comments showed no regard for others' feelings.

hobnailed 是由 hobnail（平头钉）加后缀 -ed 构成的形容词。hobnail 指靴子底部用来防滑的金属钉，hobnailed 原指"钉有平头钉的"，引申为"粗鲁的、生硬的"，形容言行像钉了铁钉的靴子一样直接生硬。