Bedikah cloth

The Bedikah cloth or a "checking cloth," called an eid in Hebrew, is a clean piece of white cloth used in the process of purifying a niddah. It is used by a Jewish woman determine whether she has finished menstruation. The cloth is inserted into the vagina, and if no blood is found, she may start counting the 7 blood-free days. On each of these days she performs this examination in the morning and in the later afternoon. If no blood is found, she may go to the mikveh on the seventh evening, and then engage in relations with her husband.

Such cloths are about two by four inches, and are available at local Judaica stores, the local mikvah, or may be cut from clean all-white soft cotton cloth.