Instead of a tangle that can fill in an area, these tangles follow a line and can be used as boarders or a line that follows your string. I have seen where some tanglers have used some of these for fill in – it’s your tangle and you can do what you want to!
Click on a picture for more information and links to instructions.
Inapod 
Betweed 
Featherfall
Tangle Addicts 