Coffee Mugs: The Bottom NotchWhy some cups have a tiny gap in the base rim

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Why it looks like that

Flip over a modern coffee mug, and you might spot a small groove cut into the circular foot ring. While it often looks like a chip or defect, this tiny channel is a deliberate engineering solution for the modern kitchen. It acts as a drainage gate, preventing water from pooling in the concave bottom when the mug is upside down in a dishwasher, ensuring dry dishes and spill-free unloading.