Here are two sites that may help you. You can also see videos on YouTube if you need to see how it is done visually.
How to mattress stitch (not only instructions but a video too:
Very helpful. Thank you.
Here is some information to help you with this. https://m.lionbrand.com/page/how-to-knit-finishing-sewing
Hi this is Peggy. Hope this helps you seam your ends together with the mattress stitch. How to Join Knitted Pieces with the Mattress Stitch
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