Although slates have been superseded in many parts of the country by clay or concrete tiles and other forms of roofing material, they are still used predominantly in some districts. Supplies have also been needed for repairs to older property. The British quarries have been unable to meet all recent demands and slates are being imported from continental quarries. Some of the continental slates satisfy or almost satisfy the British Standard BS 680, but some are of inferior quality. The testing and certification of slates are discussed.