Final answer:
The requirement for guard strips with cable in non-accessible attics pertains to the protection of nonmetallic sheathed cable from physical damage in accordance with the National Electrical Code (NEC). Guard strips need to be used when cables run across joists or within 7 feet of the floor along rafters or studding, or cables need to be protected by running boards or raceways.
Step-by-step explanation:
The requirement for guard strips with cable in non-accessible attics is addressed in the National Electrical Code (NEC). According to the NEC, when running nonmetallic sheathed cable across the top of floor joists, or within 7 feet of the floor along the sides of rafters or studding in attics, guard strips that are at least as high as the cable should be provided.
These guard strips are designed to protect the cable from physical damage, specifically from being stepped on or compressed by items being stored in the attic space.
In locations where it is not practical to maintain the 7-feet clearance, cables should be protected by running boards or installing them within a raceway when they are placed across the top of joists. Furthermore, cables must be secured and supported at specified intervals, but the exact specifications can vary based on the cable type and size, so it's important to reference the latest NEC guidelines or local codes for specific requirements.