In order to perform format conversion between the formats of a plurality of files without any work by a user, a file system stores a relation between a conversion originating file and a conversion destination file, and synchronously with an issue of a file operation API, the format conversion processes are executed. The first step in this process is to fabricate the underlying base structure and deposit an optical structure thereon. Similarly, since conventional universal colorants may be employed, the equipment utilized to tint and agitate paint in order to provide any desired color may be utilized to tint the present grout compositions. The separation torsion spring and the engagement members are disposed between the first plate member and the second plate member and maintain a constant distance between the plate members.