How to knit P3tog tbl – purl three together through the back loop

A step by step tutorial showing you the p3tog tbl knitting stitch – a right-leaning decrease for the purl side

I begin with the assumption that nobody could convince you to avoid this most complicated knitting decrease of them all. To be fair, it’s the only way to achieve a right-leaning decrease when knitting the wrong side of stockinette stitch or garter stitch in the round. So, here’s how to knit the p3tog tbl purl decrease.

a swatch decreased with p3tog tbl as seen from the right side (looks like k3tog tbl)
P3tog tbl as seen from the right side

P3tog tbl is the abbreviation for purl three together through the back loop. This double decrease is quite similar to p2tog tbl but considerably more difficult to knit. From the right side, it will look like a right-slanting k3tog or a bit like an SSK. The left-leaning counterpart is the standard p3tog, and there”s also a centered purl double decrease.

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Knitting p3tog tbl step by step

a knitted swatch decrease with p3tog tbl - purl three together through back loop as seen from the wrong side

Knitting purl three together through the back loop requires quite a bit of patience, a loose gauge, and probably good lighting. Otherwise, you risk splitting the yarn or even dropping stitches.

Active Time 1 minute
Total Time 1 minute

Instructions

  1. Loosen up the three stitches you want to decrease with your right needle.

    loosening up three stitches with the right needle to prepare the p3tog tbl knitting decrease

  2. Insert your right needle from right to left through the back loop of the stitch.

    inserting the needle through the back loop into three stitches from behind
  3. Wrap the yarn around your needle counter-clockwise.

    wrapping the yarn counter-clockwise around the needle
  4. Pull the yarn through carefully, and slip the three stitches of your left needle.

    pulling the yarn through to finish the right-leaning p3tog
    It really helps if you sort of scrape the right needle against the left needle so the yarn can't slip off as you try to pull it through.

Notes

Before you drop the stitches, make sure you really went through all three of them. It's quite easy to miss one.

It's a bit easier to purl three together through the back loop if you are using very sharp needles.

Also, be aware that this decrease tends to put quite a lot of strain on your needles. Bamboo or other wooden needles may actually break if you apply too much force. So, be careful.

Two alternative ways to knit a left-leaning double purl decrease

Now, I already mentioned that this is a very difficult decrease which I personally would avoid as much as possible. That being said, there is a somewhat easier way to achieve a left-slanting double purl decrease. Or I wouldn’t even call it easier but a bit more consistent to knit if that makes any sense.

I found two versions, and I think alternative a) is probably much easier

the right leaning purl double decrease pspsso2
Wrong side of PSPSSO2

A) Purl, Slip, Pass-Over twice (PSPSSO2)

I really like this version and I would recommend it as the standard version:

  • Step 1: Purl one stitch through the back loop
  • Step 2: Slip it back to the left needle (without twisting; just needle tip to needle tip)
  • Step 3: Pass the second stitch over the one you just slipped (a bit like a bind-off)
  • Step 4: Pass the third stitch over as well
  • Step 5: Slip the remaining stitch back to the right needle purlwise
the right side of a swatch decreases with pspsso2 - a right leaning decrease
Right side of PSPSSO2

B) Slip, Twist, P3tog

This is another version I found but it really is a pain to knit, so I’m not sure how much easier it really is. It work but that’s about it.

Step 1: Slip three stitches purlwise one at a time to the right needle without knitting

slipping 3 stitches purlwise to start the p3tog tbl alternative

Step 2: Insert your right needle into all three stitches at the same time from right to left (this will feel quite awkward) and slip them back to the left needle as one unit.

slipping the tthree stitches purlwise as a unit

Step 3: Purl these three stitches together the regular way.

inserting the needle into three stitches and wrapping the yarn around counter-clockwise

This will result in the very same decrease, though the slipping back and forth is quite a bit awkward if there are a lot of these decreases in a pattern. But at least it’s a bit more reliable than trying to wiggle through your needle through the back loop all the time.

At the end of the day, you should always check if you can’t substitute a p3tog tbl with easier stitches. Either by decreasing from the knit side or by knitting two single-decreases next to each other (for most lace patterns, the latter wouldn’t be an option, though!)

And that’s how to p3tog tbl. Feel free to comment below in case you have any questions

how to knit p3tog tbl - purl together through back loop

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