There is worse: An UK three-pin plug
These can be very bad because
The metal pins are rigid and narrow, so your body weight is concentrated onto a tiny area.
The sole of the foot contains many nerve endings, making it very sensitive to pressure.
If you step on it unexpectedly, your full weight may land on it before you can react.
People often describe it as:
A sudden, sharp, stabbing pain.
Intense enough to make them instantly lift their foot or shout.
Usually lasting from a few seconds to a couple of minutes, with soreness that may persist for hours if there is bruising.
