What should be used for protection and support of single insulated conductors?

The use of cleats and knobs is appropriate for the protection and support of single insulated conductors, particularly in residential and less complex commercial installations. Cleats are specifically designed to hold conductors in place by securing them to a wall or surface while allowing for some flexibility in the conductor's movement, which is crucial for minimizing mechanical stress and potential damage to the insulation.

Additionally, knobs can serve a similar function by acting as a physical barrier that keeps the conductors spaced apart and prevents them from coming into contact with surfaces that might cause abrasion or degradation. This method is particularly useful in environments where the conductors may not require extensive protection or where they are not in locations that are subject to harsh conditions.

In contrast, other options like raceways, PVC conduit, and cable trays are typically used for multiple conductors or offer more robust protection for conductors that may be exposed to environmental challenges or require additional mechanical protection. Thus, cleats and knobs are specifically advantageous for single insulated conductors due to their lightweight and simple support structure, making them a cost-effective solution in appropriate applications.