In addition, in CAD/QCAD 'Blocks' can be exploded to break them back down again into single entities (lines, arcs and so on). In QCAD quite simply select the block in question and
go to > Main Menu > Modify > Explode.
Essentially this is the same as 'un-grouping' in say Illustrator!
For the best support please state your operating system, QCAD version and add any supporting DXF/DWG files, screenshots etc...