a hair pencil的用法和样例：
- Susan just stood and didn't turn a hair.
- The ball missed his head by a hair.
- Didn't turn a hair during the bank robbery.
- That old man can jog10 kilometers a day without turning a hair.
- As Joe got ready to kick a field goal, the result of the game hung by a hair.
- He escaped from death by a hair's breadth.