You're right, this is a common question! And the answer is generally no, you cannot securely fasten three NM cables under a staple that only lists cable sizes and doesn't explicitly state the number of cables it's rated for.Here's a breakdown of why: Listing and Labeling are Key

The National Electrical Code (NEC) relies heavily on the listing and labeling of equipment. Electrical staples are no exception. If the staple is listed for a specific cable size (like "14/2 NM-B" or "12/2 NM-B") and doesn't say "suitable for multiple cables," then it's only approved for one cable of that size.

Secure Support

The primary function of a cable staple is to securely support the cable without damaging it. Trying to cram three cables under a staple designed for one can lead to:

Insufficient Holding Power

The staple might not be tight enough to properly secure all three cables. They could sag or pull out over time.

Cable Damage

Overtightening the staple to accommodate the extra cables can crush or damage the insulation, potentially creating a short circuit or fire hazard. The stapling could easily cut through the jackets when forced over 3 cables.

Violating Listing

Using a product outside of its listed application is a code violation.

NEC Language (Implied)

The NEC doesn't explicitly say "you can only put one cable under a staple unless it's labeled for more." However, Article 110.3(B) requires listed or labeled equipment to be installed and used in accordance with any instructions included in the listing or labeling. Since the listing doesn't state multiple cables are acceptable then you can not use it this way.

The Right Staples Exist

There are staples specifically designed and listed for securing multiple NM cables. These are typically wider and have features to evenly distribute pressure. They will clearly state on the packaging how many cables of each size they are rated for (e.g., "Acceptable for (2) 14/2 or 12/2 NM Cables").

In Summary

Don't assume a staple is suitable for multiple cables just because the opening looks* like it might fit.

Always refer to the staple's listing and labeling. If it doesn't explicitly state that it's acceptable for multiple cables of the size you're using, use a separate staple for each cable (or use a multi-cable staple).

Therefore, using a staple only listed for cable size to secure three 14/2 or 12/2 NM cables is a code violation and could create a safety hazard. Spend the few extra dollars and get the correct staples for the job. Your safety (and the safety of others) is worth it. Flag for review