垫脚石

例句：

1. 1. The old man used to use a wooden stool as a stepping stone to reach the top of the hill.
   这位老人以前用一根木凳当踏脚石爬到山顶。
2. 2. He placed his foot on the step and carefully climbed up the ladder.
   他踩在台阶上，小心翼翼地爬上梯子。
3. 3. She used her experience as a stepping stone to help others in their careers.
   她利用自己的经验作为踏脚石帮助别人在事业上取得成功。