“墙头草”和“敲门砖”分别用英语怎么说？

fence-sitter
stepping stone

墙头草
qiángtóucǎo
[fence-sitter] 比喻无主见的人、顺风倒的人
敲门砖
qiāoménzhuān
[a brick picked up to knock on the door and thrown away when it has served its purpose—a stepping-stone to success] 拣砖头敲门,门开后即弃砖。比喻谋求名利的手段