d granddaughter is a carpenter and the toilet next to the translator is what it means

The rhetorical device of rhetorical question.

Meaning: You're not a carpenter's son – so your handiwork is not good.

If the context indicates that you are doing carpentry, or want to do carpentry, this sentence is a blow to your confidence and tells you that you are not as good as you think you are, and that you are not up to the task.