Final answer:
A technician avoids using the open end of a wrench on a frozen fastener to prevent rounding the fastener. They may also use a pipe over a wrench for increased leverage, although it's a hazardous technique that can break the bolt.
Step-by-step explanation:
A technician would likely avoid using the open end of a wrench to untighten a frozen nut or bolt because it can round the fastener. Using the open end often provides less contact with the nut or bolt, and when force is applied to a very tight or frozen fastener, the wrench can slip or move, leading to the rounding of the edges. Instead, a technician would use the box end of a wrench or a six-point socket to achieve the best grip and reduce the chance of rounding.
Mechanics sometimes use a length of pipe over the handle of a wrench to increase leverage, which follows the principle of mechanical advantage. This provides more torque, making it easier to break the fastener free. However, this can be dangerous as it can also break the bolt due to the excessive force applied.