● Covered by 1 source · 1 reportLow impact1 neutral
Electrical Plug Prong Holes Primarily Aid Manufacturing, Not Outlet Grip
Key points
- Prong holes aid in manufacturing by positioning metal blades.
- Holes act as lockout tags for safety during production.
- Originally, holes engaged with detents in outlets for grip.
- UL revised standards, making detent function obsolete.
Manufacturing Utility
The holes found in electrical plug prongs primarily serve a purpose in the manufacturing process. Workers use an alignment rod passed through these holes to hold the metal blades in position before the plastic molding is applied. This ensures correct alignment of components during production.
Additionally, these holes function as lockout tags, contributing to safety mechanisms during manufacturing. This utility in production has replaced their original, more direct function in household outlets.
Obsolete Outlet Grip Function
A common explanation for the holes is that they help an outlet grip the plug. Historically, this was true; according to the National Electrical Manufacturers Association (NEMA), the holes would engage with a small raised feature, known as a detent, inside the receptacle to retain the plug.
However, Underwriters Laboratories (UL) later revised receptacle standards. These new standards required outlets to hold plugs securely without relying on the holes. Most manufacturers subsequently stopped including the matching raised features in outlets, as they no longer contributed to meeting minimum requirements and made plugs harder to remove.
✨ This summary was generated by AI from the outlets' reporting listed below. It is not independently verified and may contain errors — check the original sources. How BrevFeed works →
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Reporting from
The holes in electrical plug prongs are primarily used in the manufacturing process to position and hold the metal blades. While they once served to help outlets grip plugs, this function is largely obsolete due to updated standards and manufacturing practices.