The Non Slip Loop Knot is also known as the "Kreh Loop" and was made popular by Lefty Kreh, a fishing legend. The name says it all-this knot will not slip at the end of a fishing line and the loop connection allows for the fly or lure to have a more natural action in order to better entice fish. This type of knot is found by many fishermen to be easier to tie than the Rapala Knot, which is quite similar to the Non Slip Loop Knot. It is still as reliable too.
The Non Slip Loop Knot has a very high strength because the tag end is not just hitched once around the line that is standing. This type of knot makes a very sturdy fixed loop in the end of the line and this type of knot makes it possible to get a much more natural action. This loop is fairly easy to replicate and it doesn't catch grass or other things on the retrieve which is an added bonus.