Socket-connect fittings are easier to weld than butt-weld fittings because the fitting doesn't need to align perfectly to the pipe. Slide the pipe into the socket and weld.

Made from 4130 alloy steel, also known as chrome-moly steel, these tubes have low carbon content for good weldability. They’re often used for building frames and supports, since their flat sides make them easier to bolt than round tubes.