put your finger on

US /pʊt jʊər ˈfɪŋ.ɡər ɑːn/
UK /pʊt jʊər ˈfɪŋ.ɡər ɑːn/
"put your finger on" picture
1.

mettre le doigt sur, identifier précisément

to identify exactly what is wrong or what has caused a problem

:
I know something is wrong, but I can't quite put my finger on it.
Je sais que quelque chose ne va pas, mais je ne peux pas vraiment mettre le doigt dessus.
The manager couldn't put his finger on why sales were declining.
Le gérant ne pouvait pas mettre le doigt sur la raison de la baisse des ventes.