headless documentation

Hi devs, Is there any documentation for headless? Not that it seems completely pointless, but how exactly is it supposed to work? I'm looking for documentation that explains why, but preferably also old situation and how it should be converted into new situation kind of examples. Things like: can I simply insert into a void-headed BAT to automatically create a BAT with gaps if I e.g. insert 1, 5 and 7. Can I do a selection on the head (which should be a simple offset jump) to easily retrieve its tail, and how does the subselect interface exactly work. There appears to be not even comments on this piece of code. Regards from Fuerteventura, Fabian