What is the use of kink in clinical thermometer?

Kink  in  the Mercury thermometer helps to prevents the falling of mercury present in capillary  tube into bulb. It ensures that the user takes the correct reading of temperature.

That's  the reason a person before taking  a new reading must give a sudden shake to the clinical thermometer so that the mercury level comes to normal .

Hence Kink in mercury thermometer plays a important  role without which appropriate reading of temperature is not possible.