I'm talking about decorative slits as these were for example used in the pattern "Pfeilraupe".
I intentionally did not use the one row buttonhole technique (worked entirely in one and the same row) as this results in a very tight cast off and, for longer slits, it generally causes visible puckering. I prefer an amended two row technique with a trick.
In the right side row, I knit to the point I want the slit to start.
Directly starting with casting off will not give very neat result why I had to find a trick.
Insert the tip of the left needle into the last knitted stitch on le right needle
Bring the yarn around the left needle
and pull the thread as a loop through the stitch.
The stitch coloured in blue is the normal one and the one in green on the left corresponds to the newly formed loop.
Knit the next stitch. To avoid the previous stitch (blue) and the additional loop (red) sticking together, use your index finger to keep them well separated.
Slip now the additional loop (red) from right to the left over the last knitted stitch.
Now we created a link binding the whole as well optically as also technically together and you are ready for the normal cast off.
Cast off the desired number of stitches
and pay attention to the fact (!) that the last stitch before the marker needs also to be casted off.
Thus, take off the marker and cast off this last stitch. Knit the next stitch and tighten it very well, knit to the end.
On the wrong side row, knit to the slit and turn the work.
Now insert the right needle tip from the front into the last knitted stitch
and, with a clockwise turn (see red arrow), form a loop. This loop not only serves as first loop for the crochet cast on bit it also tightens the last stitch.
Now the first stitch can be crochet on. If you prefer, you can use a crochet hook instead the knitting needle; this may smoothen your work flow.
Crochet cast on the same number of stitches as casted off in the previous row. The loop on the right needle does not count! If the marker will be needed further, hang it in.
Turn the work
and glide the stitches on the left needle towards the needle tip. The loop (on the left needle) is used as next stitch. Now bring the yarn behind the needle and slip the stitch on the left needle after the loop from the left to the right over the loop.
The stitch resulting from the loop is slipped as to purl. Knit normally to the end.
At the end, the slit will look as follows
Nicely bound at both ends. The crochet cast on stitches are bound with the cast off stitches. Furthermore, as it is worked over two rows, no purl stitches go along the edge of the slits, which makes them look so much nicer.
You may prefer to test this technique first. I have just to say: sampling ;-) Indeed, this is likewise valuable for this kind of testing. ;-)
Thanks ♥ to Cloclo for the translation