Seguin ten boards, also called ten boards, teen boards and number boards, are used in many Montessori schools to help children begin to associate “teen” number names with their corresponding numerals. The ten boards are two boards that hold number cards. One board has the number “10” five times, and the other has it four times. They are always used in conjunction with each other. Cards numbered 1 through 9 accompany these boards and can be slipped into the slots so that they overlap the 10’s underneath.