Hi
This may seem a very silly question but I have seen a lot of projects with threads left at the front of the design why is this? And what is parking please?
Some threads are probably parked exactly where they will be used next and some will be starts and finishes that get worked over on the back and snipped off from the front. This means you never have to flip your work.
This is a good guide to parking, which should help you get clear in your mind what it's all about: http://www.scarletquince.com/parking.php" target="_blank" target="_blank.
I use this method and park in 10 stitch wide columns, working downwards. I also bring tails up to the front of the fabric to the side of the column (the parked threads are underneath the column, which is how I can tell them apart) and every now and then I flip my frame over to pull the tails through to the back, run them under and snip off. I've tried snipping from the front to totally avoid flipping my work but I couldn't get the hang of it. Hope that makes sense!