This technique for joining 2 ends of yarn without a knot, is super helpful then you run out of yarn in the middle of a row and do not want to tie a knot in your yarn!
It also allows you to avoid having to come back later and weave in ends in the middle of your project.
This is perfect for afghans, but I wouldn't do it if the join might end up in the front of a sweater. It might be ok on the back of a sweater or on a hat.
You have to be the judge of that because it does make a slightly bulkier spot in the yarn that might be visible with different types of yarn.
Give it a try and let me know how it works for you!