Borrow chickens to lay eggs and make birdcages.

Refers to the use of others or external resources to achieve their goals or improve their abilities.

The specific explanation is as follows:

-"borrowing chickens to lay eggs": borrowing other people's chickens to lay eggs is a metaphor for using other people's resources or strength to achieve their own goals;

-"Changing cages for birds": letting birds out of cages and letting better birds in is a metaphor for getting better opportunities or benefits by changing the environment;

-"Ascending to Heaven by Ladder": Ascending to Heaven by someone else's ladder is a metaphor for reaching a lofty goal or pursuing a higher realm with the help of others.

This idiom emphasizes the use of external resources and conditions to develop oneself, and to achieve oneself by timely transformation and leverage. It tells us that in the process of pursuing success or achieving goals, we sometimes need to be good at relying on the strength and opportunities of others to flexibly respond to changes in the environment, actively adapt to and strive for better development.