I have to say that until I started studying lace, I never really noticed that there were so many ways of creating a left slanting decrease (\), whereas a right slant (/) is always done using K2tog.
Then the questions came: Is there a difference between the look of a SSK, SKPO and Ktog tbl? Why are there so many different ways of making this decrease? And (just to be a devil), what happens if you slip purlwise instead of knitwise?
In the end, I decided to do an exercise to see:
The exercise has yielded interesting results. As you can see, there is a certain difference to the stitches, but not too much.
The conclusion is that it must be a matter of designer preference or convenience as to why a certain method is selected. A SKPO looks the same however you slip the stitches. SSK needs to be done properly (stitches slipped knitwise) if you want a clean-looking stitch that mirrors the K2tog panel on the other side. A purlwise SSK or a K2tog through the back loops will give you a much thicker looking slant, I think due to the twisted stitches.
Just to test my findings, I did one more exercise:
I’m afraid that my camera does not seem to like photographing detail in this wool (I think I’m going to have to change my choice of test yarn to a worsted spun that produces a crisper look). I’ve upped the contrast significantly to show up the lace twists, so I hope it looks on your screen.
The left slants in the two left hand panels are produced using a SKPO. The right hand panels are produced using K2tog tbl.
The size of the YO holes are the same in both techniques. The K2tog tbl produces a slightly straighter and fatter slant than the SKPO. But really, there’s not much difference.
My conclusion is that K2tog tbl is the same as SSK and SKPO, but you might want not want to use it if you are producing a netting-style lace, as the thicker slant is much more noticeable when used to produce a continuous line.
In terms of how this has affected my knitting, I am now able to read a lace chart without having to constantly check the key. A significant improvement from my point of view!