[Walking Eagle]

The knot campingkids is describing is called the arbor knot. To see a graphic of how it works, go to:
http://home.cfl.rr.com/floridafishing/knot5.htm

A good hard pull on a knot in 3 lb line is probably not the thing to do. Just snug it up to the spool and let the layers of line cover it up.