Are Holes in Plugs Totally Useless? Not Anymore!

Summary

This video unravels the mystery of the small holes in U.S. plug blades — dispelling myths (padlocks, cost-cutting, manufacturing alignment) and tracing their origin to early Edison-era sockets and Harvey Hubbell’s detent designs. Once used to secure plugs, the holes became largely vestigial for 75 years, but modern makers have revived their purpose with locking extension cords and adapters that use ball bearings or spring hooks to latch into the holes for a secure connection. The script explains compatibility, NEMA guidelines, and practical alternatives (knots, plug locks, Velcro), highlighting heavy-duty favorites like DeWalt and why the design endures.

Takeaways

• 🔌 The small 1/8 in (≈3 mm) holes in US plug blades have been present for decades but were largely unused for most of the last ~75 years.
• 🕵️‍♂️ Common myths about the holes include: for locks/zip ties, to save metal, or for manufacturing alignment — all are either incorrect or only occasionally true.
• 🧠 The holes originally relate back to early plug patents (Harvey Hubbell and others) where detents, slots, and holes helped secure plugs in receptacles.
• 🏺 Early electrical systems used Edison (E26) light-socket fixtures; early appliances often used bulb sockets before modern receptacles existed.
• ⚙️ Multiple inventors produced competing plug designs (tandem, parallel, detents), leading to holes becoming a simple, manufacturable standard feature.
• 🧩 By the 1950s most wall receptacles no longer included matching latching mechanisms, making the holes mostly redundant in typical home outlets.
• ⚠️ Overly secure receptacle connections can be dangerous — a plug that doesn’t break free can damage cords or devices if tripped over.
• 🔒 Modern products have repurposed the holes: locking extension cords and plug-locking accessories use the holes to create strong, reliable connections.
• 🛠️ Locking extension cords use different mechanisms (spring-loaded ball bearings, spring hooks, sliding collars) to engage the plug holes and resist pull-out forces.
• 💡 These locking cords are especially useful for power tools, yard work, construction, and any situation where plugs are frequently pulled or tugged.
• 🔁 Most plugs with holes comply with NEMA guidelines on hole placement; therefore compatible plugs generally work with these locking mechanisms.
• 🧰 Alternate, low-tech ways to secure plugs include tying knots, Velcro straps, or plug locks — but locking extension cords offer a convenient, often superior solution.

Q & A

Why do U.S. plugs have small holes in them, and what is their purpose?

The small holes in U.S. plugs were originally designed to secure the plug in place within the socket, using a latch mechanism. Over time, this feature became obsolete as receptacles stopped using this mechanism, and the holes no longer served a significant purpose. However, recent innovations have found a clever way to use these holes again, particularly in locking extension cords.

What are some common myths about the purpose of the holes in plugs?

Three common myths include: 1) The holes are for attaching locks or zip ties to prevent the plug from being used, 2) They're intended to save money by reducing metal in the design, and 3) They're used for aligning the blades during the manufacturing process. However, none of these are the actual reason for the holes.

Who invented the modern plug, and how did the holes become part of the design?

Harvey Hubble, an inventor from Bridgeport, Connecticut, is credited with the modern plug design. He patented plugs with 'detents' or indentations in the prongs to secure the plug in place, which eventually led to the adoption of the hole in the blades. These holes were added for a mechanism that would help the plug lock into place in early designs.

Why did the hole mechanism in plugs become obsolete in the 1950s?

The hole mechanism became obsolete because manufacturers moved away from using receptacles that secured the plug too tightly, as this posed safety risks. A tight connection could cause damage to the plug or the socket when cords were pulled or tripped over, so outlets evolved to use a more efficient but less secure fit.

What modern application is making use of the holes in plug blades?

Modern applications, particularly in locking extension cords, are utilizing the holes in plug blades. These cords use the holes to secure the plug in place, preventing accidental unplugging, which is ideal for tools and equipment used in tasks like yard work, construction, or cleaning.

How do locking extension cords work with the holes in plugs?

Locking extension cords use the holes in the plug blades to create a secure connection. These cords use spring-loaded ball bearings or metal hooks that pop into the holes, locking the plug in place. The locking mechanism can be released with a lever or collar, allowing for easy disconnection.

What is the advantage of using locking extension cords in certain environments?

Locking extension cords are particularly useful in environments where equipment is moved frequently or where the risk of unplugging the cord is high, such as construction sites or outdoor workspaces. The locking feature prevents cords from accidentally disconnecting, improving safety and productivity.

Do all plugs with holes work with locking extension cords?

Not all plugs with holes are compatible with locking extension cords. The plugs must have holes in the correct position, following specific guidelines set by the National Electrical Manufacturers Association (NEMA). Plugs without holes or with holes in the wrong position won't work with locking mechanisms.

What are some alternatives to locking extension cords for preventing plugs from coming loose?

Alternatives to locking extension cords include tying the cord in a knot, using external plug locks, or using Velcro straps. While plug locks provide some added protection and Velcro straps can be a low-cost option, they may not be as reliable as a locking extension cord in high-use environments.

Why might hotel lamps have poorly functioning outlets, as mentioned in the script?

Hotel lamps often have poorly functioning outlets because the sockets are often poorly designed or have worn-out components. This can result in loose connections, which make them frustrating to use. This is also mentioned as a specific example of how not all outlets are designed with durability and secure connections in mind.