He who does his own trade does not tear his shirt. The specialist who works within his competence avoids the frantic effort and damage that come from attempting things beyond one's knowledge.
The guild system of medieval Milan enforced professional specialization not merely for economic reasons but because the city had learned through repeated experience that jacks-of-all-trades produced inferior results and created social friction. The silk weaver who tried to be his own notary, the goldsmith who attempted to practise medicine, or the merchant who built his own warehouse without hiring a master builder — all tore their metaphorical shirts in the struggle against their own incompetence. The phrase captures the Lombard conviction that deep knowledge of one trade is more valuable than shallow knowledge of many, and that working within one's competence is not timidity but wisdom. The artisanal identity of the region's most successful industries — Como silk, Brescia ironwork, Bergamo textiles, Milan fashion — all rest on this principle of focused mastery cultivated over generations.
Rooted in Milan's medieval guild system that enforced professional specialization; the metaphor of the torn shirt evokes the physical cost of working against one's competence — sweat, strain, and damaged clothing.
A craftsman refusing to take on work outside his speciality
La falegnameria non è la mia cosa. Chi fa el mestee so la camisa no la rumpiss — chiama un falegname.
Carpentry is not my thing. He who does his own trade does not tear his shirt — call a carpenter.
A consultant advising a company to stick to its core business
Non espandetevi in settori che non conoscete. Chi fa el mestee so la camisa no la rumpiss.
Don't expand into sectors you don't know. He who does his own trade does not tear his shirt.
A doctor declining to give legal advice
Per le questioni legali parlate con un avvocato. Chi fa el mestee so la camisa no la rumpiss.
For legal matters speak with a lawyer. He who does his own trade does not tear his shirt.
A musician who attempted but failed at producing
Ho imparato la lezione. Chi fa el mestee so la camisa no la rumpiss — torno a suonare.
I've learned the lesson. He who does his own trade does not tear his shirt — I'm going back to playing.