What is the best sewing stitch to mend flannel sheets?

http://chestofbooks.com/crafts/needlework/Clothing...

What you've got is called a three corner tear or square tear. Unfortunately, it's a sign that the fabric is probably not of particularly good quality, so don't be surprised to get more of the same later.

I would probably start by ironing a scrap of fusible tricot interfacing over the tear, then machine mending through the tricot.

i always use my double zig zag