P2tog & SSP and P2tog tbl & SSP tbl

On the knitting board, the p2tog and ssp (or p2tog tbl and ssp tbl) are paired together, one being done on the bottom rake and the other on the top or vice versa. This is done to ensure that the slant of the decrease is correct on each side of the fabric. A description and direction for each decrease is given below. The easiest way to set up the knitting board is to setup the stitches on the bottom rake and then turn the board and set it up the same way. So, work a P2tog stitch on the left bottom rake and a SSP stitch on the right bottom rake, turn the board and repeat. If you are using p tbl stitches, work a SSP tbl stitch on the left bottom rake and a P2tog tbl stitch on the right bottom rake.

Purl Two Together (P2tog) /
Purl Two Together through the back loop (P2tog tbl)

P2tog is a right slanting decrease stitch in which two stitches are purled together. P2tog tbl is a left slanting decrease stitch in which two stitches are purled together through the back loop. On the loom this means picking up one wrap, putting it on the peg on either side (depending on the stitch), wrapping the peg as you normally would and then knitting off. See the purl stitch and p tbl stitch if you are not sure how to purl.

This stitch is more common in needle knitting since loom knitting is all done on the RS.

Slip Slip Purl (SSP) /
Slip Slip Purl Through the Back Loop (SSP tbl)

The SSP stitch is a left-slanting decrease that mirrors the P2tog and is worked with the purl stitch. SSP tbl is a right slanting decrease stitch that mirrors the P2tog tbl and is worked with the P tbl stitch. To do an SSP or SSP tbl on the loom, you will need to pick up one wrap and hold it with your knitting tool, move the wrap from the peg on either side (depending on which stitch) to the empty peg and the replace the wrap being held on the knitting tool back onto the peg.

This stitch is more common in needle knitting since loom knitting is all done on the RS.