I already referred to the hidden stitch and I will in some of my upcoming tutorials, therefore I made this easy tutorial on the hidden ladder stitch.
The hidden stitch is used when you need to close an opening and not let the thread be seen. Typically when you sew two layers together the wrong sides out and need to leave an opening through which you turn the fabric then right sides out. Use a matching thread, I used a contrast one to make the process better visible.
The fabrics you are stitching together should have folded and ironed edges. They are places wrong sides together.
First, pull the thread from the inside to the outside.
Then pass the needle in the opposite fabric and exactly opposite to the hole through which the thread exited the first fabric. Then pass the needle about half a centimeter away from the second hole but staying in the same fabric.
To create the ladder effect now pass the needle back through the first fabric (again opposite to where it has just exited the second fabric) and then pull the thread out half a centimeter away in the same fabric.
Repeat the steps…
…until you have closed the whole opening.