暖簾に腕押し
Meanings
1
futile effort; like pushing against a curtain
Idiomatic expression meaning that an action is pointless or has no effect, like pushing your arm against a shop curtain (暖簾) which just gives way. Often used when arguing or competing with someone who doesn't respond.
No matter how much you complain to him, it's like pushing against a curtain.
Arguing with that boss is futile; nothing changes.