વાણીઆની ગત વાણીઆ રમી જાણે.

vāṇīānī gata vāṇīā ramī jāṇē.

Literally: The Vania's ways are known to the Vania.
What it means: Only someone of the same profession or background can truly understand the tricks of their trade.

Also said as

ગુજરાતી કહેવતસંગ્રહ (Gujarati Kahevat Sangrah) (1923) · read from the scan by machine — the Gujarati itself is unchecked · English is machine-made and nobody has checked it yet

Heard it differently, or know we've got the sense wrong? Tell us — that is exactly the kind of correction this needs.