The entrance to the Shrieking Shack is protected by The Whomping Willow, a very valuable, and "violent" tree planted on the grounds of a certain "school of wizardry". The Willow would attack anyone who came within reach of its branches. There was a particular knot on the trunk which can be pressed using a long branch in order to stop the attacks. However, a flying Ford Anglia crashed into it, knocking over and killing the Whomping Willow, but still, the Willow disguises the entrance to the Shrieking Shack. Either way, an "Immobulus" charm could be a valuable tool in searching for the Shrieking Shack.