This technique can be used to tie your scraps together or to add more string to a project when you run out. This knot is very strong and won't fall apart while you're working if done correctly.
Step 1
Put your old string next to your new string. Don't stretch the string. If your old string is part of a project and you don't have much string left, undo some of your work first so that you have room to tie the knot.
Step 2
Grab both ends at the same time, then create a small loop. A smaller loop will leave behind a smaller tail, letting you use more of the string, but don't make it so small that you can't comfortably work with it.
Step 3
Put the ends through the loop.
Step 4
Use your free hand to pull the ends through the loop. Pull both sides outwards. Make sure you're pulling tightly on both pieces of string at the same time. If your tail is a little too big, you can start by pulling loosely, then using your thumb to nudge the knot before you pull tightly.
Step 5
Now, you will tighten the knot. This helps make it smaller and more secure. Pull the top-left and the bottom-right strands at the same time.
Step 6
Pull the top-right and bottom-left strands at the same time.
Step 7
Cut the short end. I would not recommend cutting any shorter than my example or else you risk the knot falling apart while you're working.
Hope this was helpful! I went pretty slow with this tutorial, but once you get familiar with this knot, you can do it in seconds!