The phrase "steel fittings" refers to items made of steel that are used to join or connect different objects or parts together. These fittings are usually strong and durable, as they are made of steel. Full definition
Install high pressure engineered carbon and stainless steel fittings for the transfer of liquids and gas. (livecareer.com)
U.S. Secretary of Commerce Wilbur Ross announced the affirmative preliminary determination in the countervailing duty (CVD) investigation of imports of forged steel fittings... (commerce.gov)
The works onsite are assisting Steel Fitters onsite, loading / unloading materials, site clearing, skipping and other associated tasks. (cv-library.co.uk)