stock-in-trade
1. The goods or equipment that a particular professional, company, industry, profession, etc., uses or deals in for business. You should talk to Sarah if you're looking to buy a new laptop—computers are her stock-in-trade, after all. Art supplies are my stock-in-trade, so I know just about all there is to know about paint.
2. By extension, the traits, characteristics, or behaviors that typify or are readily called upon by a particular person or thing. Witty humor has always been his stock-in-trade. A good imagination is the stock-in-trade of any good writer.
stock in trade
whatever goods, skills, etc., are necessary to undertake an activity of some kind. Of course I am glad to help. Packing household goods is my stock in trade.
stock in trade
One’s capabilities and resources. This cliché transfers the original meaning of the phrase—that is, the goods for sale kept by a dealer, or the tools kept by a workman—to more personal attributes. Thomas de Quincey used it in Cicero (1842): “Such charges were the standing material, the stock in trade of every orator.”