There are two versions of Bonehilda in the game. One is the janitor on the Magic Town lots A Spooktacular Spot and Vernon's Vault. The other can be bought on residential lots as a magical (and much cheaper) equivalent of Servo. This version of Bonehilda is literally a "skeleton in the closet". If the "skeleton maid" version of Bonehilda is in her closet, clicking on the closet will give the "Knock" interaction. Selecting this will cause the selected Sim to go to the closet and knock on it, which will bring Bonehilda out to do chores. The selected Sim does not have to have magic to do this.