Subject: How do you cleanly remove the bottom of a wine bottle

My dad used to do this all the time - I remember him putting something in the 
bottle to the height he wanted the break and then I dont remember what he did 
next but the bottle was cleanly separated wherever the line of the liquid was 
that he put in it.  Do you know how to do this??

Re: How do you cleanly remove the bottom of a wine bottle