When you speak of bad luck, it is said that one should always knock on wood. Also knocking when speaking of good luck apparently helps with having good luck. This is an old Celtic tradition related to belief of wood spirits.
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An acorn at the window will keep lightning out
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Placing a hat on the bed is, apparently, bad luck. (South Carolina)
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According to an age old custom, carrying a dead shrew in your pocket wards off rheumatism!
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A single magpie is considered a sign of bad luck. A Guide to the Scientific Knowledge of Things Familiar recites an old proverb concerning the incidence of bad weather when magpies forage alone and a possible scientific explanation for this.
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In some parts of England, rum is used to wash a baby's head for good luck.
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Placing keys on a table is considered unlucky. (Sweden)
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Some motorcycle enthusiasts hang a biker's bell from a portion of their bike to protect themselves from evil road spirits.
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