nail (your) colours to the mast
to publicly state your opinions about a subject.
Nobody knows which way he's going to vote because he has so far refused to nail his colours to the mast.
英语词组固定搭配大全包含18674条英汉双解词组,基本涵盖了全部常用英文词组、短语的翻译及用法,是英语学习的有利工具。