Which of the following schedules does not show the voltage of the listed items?

The choice indicating "Hardware" is correct because it typically includes items such as bolts, screws, and connectors, which do not have a voltage rating associated with them. Voltage ratings are relevant for electrical components that conduct or manage electrical current, such as switches or circuit breakers.

In contrast, materials, labor, and tools can involve voltage-related considerations. For example, tools may be rated for specific voltages if they are powered electrically, and materials can refer to wiring or insulation, which also have defined voltage ratings for safety standards. Hence, "Hardware" is the appropriate selection as it does not pertain to voltage specifications.