This style file implements chapter headers in sans-serif and bounded by 
lines \textwidth wide, both above and below the header itself.  I have 
created and used that style to typeset a 300-pages book about statistics 
in physics; and it turns out that, from time to time, somebody needs 
headers looking like that and asks for them on comp.text.tex .

(The comments at the beginning of bsheaders.sty are exhaustive.)