A weler (also weldor, which term distinguishes the tradesman from the equipment used to make welds) is a tradesman who specialises in welding materials together. The materials to be joined can be metals (such as steel, aluminum, brass, stainless steel etc.) or varieties of plastic or polymer. Welders typically have to have good dexterity and attention to detail, as well as some technical knowledge about the materials being joined and best practices in the field.