The Danish New Year's Eve tradition of smashing old plates against friends' and neighbors' doors is called plate smashing.
People who observe the custom throw unwanted crockery at the outside of a friend's or neighbor's home. A large pile of broken plates is traditionally interpreted as evidence that the household has many friends willing to visit and take part in the ritual. The objects are normally old or unwanted rather than valuable tableware.
The practice is one of several Danish New Year's customs involving noise and symbolic renewal. Other celebrations may include jumping from a chair at midnight to “jump” into the new year and watching the monarch's annual New Year's speech. Customs differ between households, so plate smashing is not a universal requirement in Denmark.
The tradition is sometimes described as throwing plates through doors, but the usual image is crockery being broken against the exterior of a home. Modern concerns about cleanup and safety mean that some people celebrate the custom less literally.