The slip slip purl, or SSP, creates the same left-leaning decrease as the SSK (slip slip knit), but it is done on the wrong side of the work. On the right side of the work, the result of an SSP looks the same as an SSK, decreasing 2 stitches to 1.
The SSP is not as common as the SSK, but it can be used in the same way for shaping garments like cardigans or lace patterns that are worked flat. Use of this decrease on the wrong side of the work might be accompanied by purl 2 together (P2tog) for a more symmetrical look.
There are different ways to complete an SSP, but here we're demonstrating the most basic technique to decrease stitches using this method.
Slip knitwise from the left needle
Slip the first stitch knitwise from the left needle to the right side needle. Repeat the same step with the next stitch, slipping it knitwise.
Slip both stitches back, purlwise
Insert left needle tip into both stitches on the right needle as if to purl, and slip them back over to the left needle. If it feels a little tricky, it's ok to slip each stitch one at a time, just make sure to do it purlwise.
Purl through the back loops
The real challenge is to purl both stitches through the back loop. It can make it a little easier to see what's happening by tipping the work towards you so you can see the back. Insert the right needle into the back legs of the two stitches on the left needle as if to purl. Purl those two stitches together. Well done!