This distinction is key, as one cannot rotate a flat-head screw with a cross-patterned Phillips head tool nor use a flat-head driver with a Phillips screw. But why have two different kinds of ...

Second, the driver won’t slip out even at high levels of torque. The Canadian Model T Ford used over 700 Roberson screws. A Phillips driver, although those screws look suspiciously like Robertsons.

The additional contact points spread the driving torque and prevent the kind of “cam-out” you get with Phillips or ...