noun
stock-in-trade; tools of the trade
Refers to the essential equipment, goods, or skills that a person uses in their profession or business. Can be used literally for physical tools or figuratively for knowledge and abilities.
料理人にとって包丁は商売道具だ。
For a chef, a knife is a tool of the trade.
彼の商売道具は
His stock-in-trade is just a laptop and a smartphone.