psso

In hand knitting, pass slipstitch over (psso) is a decrease technique used to remove one stitch from the working row. You slip one stitch knitwise or purlwise onto the right needle without knitting it, knit the next stitch normally, then use the left needle tip to lift the slipped stitch over the knitted stitch and off the needle. The result is one stitch decreased and a small diagonal line that leans left on the fabric.

The move appears constantly in garment shaping: raglan armholes, sweater neck ribbing, sock toe closures, and mitre corners all rely on psso. It pairs with knit two together (k2tog), its mirror decrease that leans right, to create balanced, symmetrical tapers. Because psso requires a separate step before the actual decrease, it is slightly slower than k2tog but gives the knitter precise control over which stitch sits on top of which.

Variations and tension

The abbreviation sometimes appears as slip 1, knit 1, pass slipped stitch over (s1, k1, psso) in patterns, which is the full written form. When a pattern calls for decreasing more than one stitch at a time, knitters may work psso twice or use a variant like s2tog (slip 2 stitches together as one). The tension of the slipped stitch itself matters: too loose and the decrease looks sloppy; too tight and it restricts the yarn flow and can distort the fabric around it.

Because the slipped stitch is never knitted, it does not pick up yarn in the normal way. This can create a slightly denser, more elastic edge to the decrease line compared to k2tog. In lace knitting, this property is sometimes exploited deliberately; in everyday garments, most knitters aim for the decreases to be invisible or at least uniform. The abbreviation psso has become standard in English-language patterns since at least the mid-twentieth century.