木已成舟　

◎ 木已成舟 mùyǐchéngzhōu

[what is done cannot be undone;the wood is already made into a boat] 樹木已經(jīng)制造成舟楫。比喻事已定型,不能改變

如今木已成舟,也是林兄命定如此。——《鏡花緣》