“One of the prime elements of the Passover Holiday is the removal of leaven products, known as ‘Chametz’ from one’s possession. ‘Chametz’ is defined as any product from wheat, barley, rye, oats or spelt which was allowed to rise, e.g. bread, crackers, etc.
This is accomplished in two ways: outright disposal of all Chametz products in one’s possession, or sale of those products to a non-Jew. [It is preferable to consume all actual chametz before Pesach, but we still perform the sale to cover any doubtful/unknown ownership].
The sale of the Chametz property to the non-Jew involves many complexities in Jewish law and should be administered by a competent Rabbi… Throughout the Passover holiday the non-Jew has full possession of the property, and has the right to take any of the Chametz for his personal use. He does occasionally exercise this right.
These procedures ensure that the Jew has completely removed Chametz from his possession for the duration of Passover.”