If you bind off (cast off) in the round, usually you end up with a bump at the last cast-off stitch. Here's a way to minimize the transition and have a smoother joint.
Bind (cast) off stitches using your preferred method until you have 1 stitch left on the right-hand needle.
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1. Insert the right-hand needle into the 1st cast-off stitch, picking up both of the top loops.
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2. Yarn around needle
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3. Pull yarn through all loops on needle
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4. Cut yarn and weave in end
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