To protect cables or tubing likely to be penetrated, a steel sleeve or plate must be at least ________ in. thick.

The correct thickness for a steel sleeve or plate designed to protect cables or tubing from physical damage is one sixteenth of an inch. This specification is significant because it provides adequate protection in environments where the cables might be vulnerable to mechanical impacts or penetrations. A sleeve or plate of this thickness is generally sufficient to absorb impacts or resist penetration while complying with safety standards and electrical codes.

In practice, using a protective measure of one sixteenth of an inch ensures that the cable or tubing is safeguarded against incidental damage that might occur in the surrounding environment. It strikes a balance between being robust enough for protection and not being excessively heavy or cumbersome. Understanding when and how to implement such measures is crucial for ensuring both safety and compliance with regulations in electrical installations.