This specification establishes the criteria for the acceptance of vitrified clay liner plates used to protectively line or face pipe, culverts, abutments, structures, or appurtenances. Linear plates manufactured shall be known as curved linear plates or flat liner plates. These plates shall be manufactured from fire clay, shale, surface clay, or a combination of these materials that, when formed into liner plates and fired to suitable temperatures, yield a product that is strong, durable, serviceable, and free of objectionable defects. The absorption of liner plates shall not exceed 6%. The liner plates shall be subjected to acid resistance test. These liner plates shall be uniformly vitrified throughout their thickness and have a homogeneous structural texture.