Many electrical plugs feature two small holes on their prongs, and these seemingly minor details actually serve important safety and practical purposes.

Electrical plugs typically come with either flat (Type-A or Type-B) or round prongs. On many flat prongs, you will notice small circular holes near the tip. Most consumers tend to overlook these holes or are unaware of their purpose.

In fact, these two holes help the plug stay securely in the socket. Standard electrical outlets often have small protrusions inside that fit precisely into these holes, ensuring a tighter connection between the plug and the metal contacts inside the socket. This reduces the risk of loose prongs and electrical leakage, making flat-prong plugs a safer option—especially in homes with young children—by helping prevent accidental electric shocks.

Historically, plugs were designed with indented grooves on their prongs. However, these grooves created friction when inserting the plug, sometimes leading to sparks and short circuits. Replacing the grooves with holes minimized this friction, making plugs safer and easier to insert without the risk of electrical arcing.

Additionally, manufacturers sometimes use the holes to attach seals, allowing consumers to distinguish between new and previously used products. Despite their small size, these holes also help save a significant amount of steel in mass production, which is particularly valuable in large-scale manufacturing.

The invention of these prong holes dates back to Harvey Hubbell Jr., who worked extensively to make plugs easier to insert. His initial solution involved small indentations that would align with corresponding bumps in the socket, but eventually, these indentations were replaced with holes while retaining the original concept.

There are primarily two types of flat-prong plugs that use holes: Type-A plugs with two flat prongs and Type-B plugs with two flat prongs plus a round grounding prong. These plug types are common in the United States, Canada, Japan, and several other countries, following the NEMA standard. In contrast, many European and Asian countries still use round-prong plugs, which do not require holes because the prong-and-socket design provides sufficient grip.

Choosing Safe Electrical Outlets and Plugs

When purchasing plugs and outlets, many people overlook the importance of selecting high-quality products. Low-quality outlets can cause a range of hazards, including electrical arcing, fires, and damage to household appliances like refrigerators, washing machines, and televisions. Over time, poor-quality outlets may also melt or deform, creating further risk of electrical accidents. To ensure safety, consider the following guidelines:

1. Buy from reputable stores: Always purchase plugs and outlets from official retailers. Look for materials that are fire-resistant and heat-tolerant, such as ABS or PVC plastics.

2. Check the power rating: Evaluate the total power consumption of devices you plan to connect. For high-demand setups, choose outlets with higher power ratings and built-in breakers that automatically cut off electricity when overloaded.

3. Inspect the product: Ensure there are no cracks, exposed wires, or other defects. Selecting products with a warranty or insurance coverage can provide additional protection.

4. Follow safe usage practices: Always handle plugs by the body, not the cord, when unplugging. Avoid placing outlets in damp areas, and regularly check plugs and sockets for wear or damage.

By understanding the purpose of these small prong holes and following proper safety practices, households can greatly reduce the risk of electrical accidents, protect their appliances, and create a safer environment for children.