A special rule created by federal government to deal with door to door or pressure sales. It allows the purchaser to cancel a contract within a short time period after signing the agreement, usually three days. (Hence the 72 hour rule which this law is also known.) The rule does not apply to sales in general areas such as a store or at a trade show. The three day rule also extends to home improvement loans and second mortgages and various states also have other applications for this rule, including the purchase of time share property.