Right Slanting Decrease (Knit 2 together from the “top”/front)
A right-slanting decrease (k2tog in English books) is knit two together from the “top” or through the front loop. This is the most basic decrease in knitting.
With “grandmother’s knitting,” this would be like knitting through the back loops, except that the stitches are turned around so now you’re knitting through the fronts. This creates a decrease that slants to the right, but with the old-style Lithuanian stitch orientation, the stitches are twisted. Depending on the yarn texture and color, this may or may not be noticeable in the finished knitting.
Left-slanting Decrease (Knit 2 together from the “bottom”/back)
Left-slanting decreases can be made in several different ways.
The oldest left-slanting decrease in knitting seems to be slip 1, knit 1, pass the slipped stitch over. I used to think this was weird because it’s three steps to make one stitch and why not use ssk or k2tog-tbl instead. Then I started knitting fine lace a lot and found that sometimes, especially with cotton or silk, skpo is actually much easier.
Ssk, sometimes called “slip, slip, knit,” is actually a variation of knitting 2 together through the back. The slips are done knitwise to change the orientation of the stitches. Then the two slipped stitches are placed back onto the left needle and knitted together through the back. A shortcut to that last part is to insert the left needle into the fronts of the two slipped stitches while they are still on the right needle and then knit them together. You are still knitting them together through the back. This was used a lot by Barbara Walker and Elizabeth Zimmermann.
Knitting two stitches through the back is really the simplest way to make a left-slanting decrease but it does twist the stitches. So depending on your yarn, project, and level of perfectionism, you may not like it. This was used by Dorothy Reade and is used by the Oomingmak knitters of Alaska, that I wrote about in a couple of my books.
To have a left-slanting decrease that looks not twisted actually only requires turning the first stitch around because the second stitch will be hidden behind it. So you can also do this: insert the right needle into the first stitch knitwise, then into the second stitch through the back loop, and knit them off together. I forgot where I learned this but I really like this one because it’s a quick one step process and still gives you a visibly untwisted decrease.
All of this assumes you have a “standard” stitch orientation with the leading leg in the front of the needle. In other words, the leg of the stitch that is in front of the needle, closest to the knitter, is also the leg that is closest to the tip of the left needle.
In general, when you knit 2 together through the front you get a right slanting decrease and when you knit 2 together through the back you get a left slanting decrease. Depending on how your stitches are oriented on the needles before you work the decrease, you may want to turn one or both stitches around before knitting them together to avoid having twisted stitches.
I find k2tog-tbl to be easiest.
With the old-style Lithuanian stitch orientation (aka “grandmother’s knitting“), the stitches are turned, so you just put the right needle into the back of the two stitches to knit them together and the final decrease leans to the left. Basically this is k2tog-tbl, but the stitches aren’t twisted.
An Alternative Decrease Method
Here’s an alternate way to decrease. This would be k2tog in American knitting, or to reverse it for combination knitting would be ssk. But in this case only the second stitch is turned around. The first stitch, which will be the bottom stitch in the decrease and hidden, is not turned.