What is the name of the joint used when joining 2 pieces of metal at a 90-degree angle?

The correct answer is "corner joint." A corner joint is specifically designed to join two pieces of metal at a 90-degree angle, which is commonly needed in various structural and fabrication applications. This type of joint provides stability and strength at the junction of the two metal pieces, making it essential for constructing frames or structures where a right angle is necessary.

The corner joint can be welded, bolted, or otherwise fastened together, ensuring that the pieces remain aligned and secure in their intended position. This configuration is utilized frequently in metalworking and construction to create sturdy corners or edges in metal assemblies.

While other joint types such as lap joints and butt joints serve specific purposes, they do not necessarily focus on achieving a right angle as effectively as a corner joint does. Lap joints involve overlapping pieces, and butt joints connect the ends of two pieces but can be at any angle. T-butt joints are typically used when one piece is perpendicular to the other but involve specific configurations that are not exclusively at a 90-degree angle at the ends of the joined pieces.