system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some electrical prongs have holes and some do not?

What purpose does it serve?
gpt
If you were to take apart an outlet and look at the contact wipers that the prongs slide into, you would find that they have bumps on them. These bumps fit into the holes so that the outlet can grip the plug's prongs more firmly. This detenting prevents the plug from slipping out of the socket due to the weight of the plug and cord. It also improves the contact between the plug and the outlet.