Professor, why couldn't we just Apparate directly into your old colleague's house?' 'Because it would be quite as rude as kicking down the front door,' said Dumbledore. 'Courtesy dictates that we offer fellow wizards the opportunity of denying us entry.
J. K. RowlingThey run off eckeltricity, do they?" he said knowledgeably. "Ah yes, I can see the plugs. I collect plugs," he added to Uncle Vernon. "And batteries. Got a large collection of batteries.
J. K. Rowling