My pattern calls for me to decrease my seed stitch border. I have six stitches of seed stitch on both sides of a stockinette stitch. I need to decrease on one side until I eliminate the border. How do I do that and still keep the seed pattern? Which decrease should I use?
Also, how do I know whether to use a right-slanting decrease or a left-slanting one?
Your questions raise several questions in my mind for you. What are you making, and what part of the project is this relating to? Are you wanting to decrease at the beginning of a row or the end, or at the inside edges of the seed stitch. Where exactly? For instance it would not be any problem to decrease at the beginning or end. You could keep in pattern by merely working 2 together either knit or purl to keep sequence with what would come next. But I’m guessing it is more complicated than than. 
Could you tell more what the actual situation is. Decrease every row or what?
I am making a shawl/cape that is made by two halves joined together. I’ve come to the part where I need to shape the back point. The pattern says to decrease 1 stitch at the beginning of every knit row on the left inside edge. This will eliminate the seed border on one side.
Do the decrease just inside the seed stitch border. A decrease (or increase) at ‘the edge’ doesn’t have to be right in the edge stitch, it can be a few stitches in.
Thanks!
Which decrease would you recommend? K2tog? Or SSK? Can I purl two stitches together?
yes you can purl 2 tog.
I would use k2tog and p2tog. Ssk you will probably not want, really, since you want all decreases to slant the same direction to keep it orderly.