This type of drive, recognizable by its square-shaped recess, is commonly used with fasteners designed for high torque applications. A Robertson drive, for instance, employs this distinctive square recess. A common size within this drive system is Number 2.
The robust design of this drive type minimizes cam-out, a phenomenon where the driver slips out of the fastener head under stress. This characteristic makes it ideal for power tools and situations requiring substantial turning force. Its development addressed shortcomings of slotted drives prevalent in the early 20th century, significantly improving fastening efficiency and reducing worker fatigue.