Centred Double Increase (CDI)
A centred double increase adds two stitches in the column of one — perfect for shawl spines, mitten thumbs, and any radial shaping that needs to expand on both sides of a centre stitch.
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Method
Knit into the front, back, and front again of the same stitch. Result: three stitches from one, with the centre stitch sitting directly above the original column.
Visual effect
Creates a clean centred column of increases that runs vertically up the work. Often used as the "spine" of a triangular shawl, where the increase produces a line of paired increases on either side of a single centre stitch.
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Pairing with markers
Place a stitch marker on either side of the centre stitch. Work increases on both sides of the marker pair on every right-side row, with a centred double increase in the centre stitch every two or four rows.
Variations
Substitute a yarn over before and after the centre stitch for an open, decorative version. The visual lines are the same; the open version reads as lace and the closed version reads as solid stockinette.
Abbreviation reference
| Abbreviation | Meaning |
|---|---|
| CDI | centred double increase |
| k | knit |
Tips
- Use a stitch marker on either side of the centre stitch to keep the increase column straight.
- Pair with garter or stockinette spine for crisp triangular shawls.
- For an open lace version, replace the centred double increase with yo, k1, yo.
In depth
A centred double increase produces two new stitches symmetrically on either side of the original stitch column. The original stitch becomes the new centre column, with the two new stitches forming the left and right "wings." This is why it works so well for shawl spines.