Why do some heavy-duty screwdrivers have a square shank?

Heavy-duty screwdrivers often feature a square shank to facilitate turning with a wrench. The square shape provides a larger surface area that can be easily grasped by a wrench, which allows for applying greater torque when loosening or tightening screws or fasteners. This is particularly advantageous in situations where a high level of torque is necessary, such as when dealing with stubborn or tightly fastened components.

The design of the square shank not only enhances the tool's versatility but also enables users to apply more force than they could with only hand rotation, making it easier to work in challenging environments or on difficult fasteners. The ability to use an additional tool, like a wrench, effectively maximizes the screwdriver’s capability and efficiency, which is especially relevant in industrial applications.

While other benefits, such as better grip or slippage prevention, may be associated with certain screwdriver designs, the primary reason for a square shank in this context is to accommodate the use of a wrench for increased torque application.