What term describes the unthreaded portion of a screw's shank?

The term that describes the unthreaded portion of a screw's shank is grip length. Grip length refers to the section of the screw that is designed to hold materials together without involving the threaded portion, which provides the fastening action. This unthreaded segment is crucial for ensuring that the screw properly engages with the material it is fastening, allowing for effective clamping force.

In contrast, the other terms relate to different aspects of the screw's dimensions. Shank length generally encompasses the total length of the screw's shank, including both threaded and unthreaded parts. Working length typically refers to the length of the screw that is effective for fastening once installed, which might include both the threaded and unthreaded portions. Threaded length would specify only the portion of the screw that has threads, which is not what is being asked in this case. Understanding these distinctions helps clarify the specific role of each part of a screw in fastening applications.