Horseshoes.
Reading edition
An ancient superstition existed that horseshoes kept witches out of the house. It was a common practice to nail them to the threshold, stipulated, however, that the shoe was to be one that had been found. In Gay's fable of "The Old Woman and her Cats," the supposed witch makes the following complaint:—
"—Crowds of boys Worry me with eternal noise; Straws laid across, my pace retard; The horseshoe's nailed (each threshold's guard); The stunted brooms the wenches hide, For fear that I should up and ride."