Simpson A21 angle is a multi-purpose angle designed for making strong and straight corner joints. Creating a solid 90 degree angle by using screws and nails alone can be difficult to get straight and becomes time consuming. The Simpson A21 can save you time and frustration by easily making that perfect 90 degree angle. Whether you're building a dog house, garage storage or shelving units, the heavy duty 18 gauge steel will hold up to create a strong and reliable connection that lasts.