passer un sapin

To trick someone into a bad deal

Usually heard as 'se faire passer un sapin', to get swindled, it's about being conned or fobbed off with something worse than what you paid for.

Il s'est fait passer un sapin en achetant cette voiture soi-disant neuve.

He got conned buying that supposedly new car.

Fir wood cracks as it dries and was worth much less than other timber, so slipping someone fir instead of a better wood in a lumber deal became shorthand for cheating them.

Quebec