What is the second hole in the sink for?

In fact, when the sink reaches full capacity, either because the drain pipes are blocked or the water flow is too strong to drain through the main sewer, the second outlet comes to the rescue. This blockage is solved by a very clever device. Whenever a certain water level is exceeded, this outlet acts as a good emergency exit: it causes the excess water to drain away, preventing the bowl from overflowing. Furthermore, this is called an “overflow” because it occurs when the water is full. These plumbers are very clever, you can confirm this.