The BLOCKS section of the DXF file contains all the block definitions, including anonymous blocks generated by the HATCH command and by associative dimensioning. Each block definition contains the entities that make up that block as it is used in the drawing. The format of the entities in this section is identical to those in the ENTITIES section. All entities in the BLOCKS section appear between block and endblk entities. Block and endblk entities appear only in the BLOCKS section. Block definitions are never nested (that is, no block or endblk entity ever appears within another block-endblk pair), although a block definition can contain an insert entity.
External references are written in the DXF file as block definitions, except that they also include a string (group code 1) that specifies the path and file name of the external reference.
The block table handle, along with any xdata and persistent reactors, appears in each block definition immediately following the BLOCK record, which contains all of the specific information that a block table record stores.