How you lace up the loop to loop knot makes a difference. You first slip the first loop into the second loop, then thread the tag end thru the first loop and pull tight. That way the complete knot looks like a square knot in profile, square knots are fairly easy to untie if you push on them just right.
http://1.bp.blogspot.com/-849ODG6eDR...handshake4.gif


The wrong way is to pass the tag end thru its self, this makes a sheeps head knot that is hard to undo.
http://www.geospectra.net/kite/knots/knot09.jpg