You can call the square screw bits as square recess bits. They’re sometimes called as Robertson because a Canadian named Robertson invented the model. These bits are typically designed for screws with a square recess in the head. There are many types of screw bits you can find online. Each has a different property and use. You can buy all of them or either one of them. But, remember, you might find it difficult to complete your projects using one single type of screw bits.