Seam for Garter Stitch

Hi all, I am knitting a hat, and I accidentally did Garter stitch rather that stockinette stitch. I am doing it on two straight single pointed needles and plan to stitch a seam in the back. I need a stitch like the Mattress stitch, but one that works with Garter rather than stockinette.

Thanks -Andrew

There is info here about seaming garter stitch. :thumbsup:

Thank you so much Jan.