The s2kpo decrease is a double decrease, which means that it reduces the number of stitches on your needles by 2.

You may see the technique abbreviated to s2kp or sl2tog k1 psso instead, and it stands for 'slip 2 together, knit 1, pass slipped stitches over'. Not to be confused with the sk2po, which is a slightly different double decrease.

As mentioned in the title, this decrease is a centred double decrease.

What this means is that, unlike most other decrease techniques, it doesn't lean either to the left or to the right; it's quite symmetrical. Because of this, it usually features on its own in a row of knitting rather than being paired up with other decrease methods to balance it out.

The s2kpo is worked over 3 stitches, and these 3 stitches get reduced down to just the 1 central stitch during the process of moving from the left needle to the right needle.

Please take a look at the tutorial here: