2.3.2 Free Chunk List
The free chunk list specifies a list of unused storage blocks in the file. The free chunk list consists of a sequence of one or more FreeChunkListFragment structures (section 18.104.22.168). The location of the first FreeChunkListFragment structure is specified by a Header.fcrFreeChunkList (section 2.3.1) field. When writing into any of the storage blocks specified by fcrFreeChunk the free chunk list MUST be updated to reflect the change.