SSSP (slip, slip, slip, purl) is a double decrease and a mirror image of P3tog, decreasing your total number of stitches by two.

 

How to work a SSSP decrease

So I have cast on 10 stitches and worked a few rows in stocking stitch, on the next purl row the instructions are :

Purl to last 4 stitches, SSSP, P1.  (8 sts)

I have purled to the last 4 stitches of the row and am now ready to work SSSP:

Step 1

Step 1 – Slip 1 stitch knitwise from the left hand needle to the right hand needle, slip the next 2 stitches on the left hand needle to the right hand needle (one at a time) in the same way as the previous stitch.

 

Step 2

Step 2 – Slip the 3 stitches back onto the left hand needle, by inserting the left hand needle from left to right.

 

Step 3

Step 3 – Insert the right hand needle through the back loops of the 3 slipped stitches (from left to right).

 

 

Step 4

Step 4 – Pass the yarn around the back, up and over the front of the right hand needle (as you would if you were purling a normal stitch) .

 

Step 5

Step 5 – Pull the yarn through the three stitches, slipping them off the left hand needle.

A double descrease completed.