kfb — Knit into front and back of stitch (Abbreviation)
kfb stands for "knit into front and back" — an increase worked by knitting into a stitch normally without sliding it off the needle, then knitting into the back loop of that same stitch before finally letting it drop off, turning one stitch into two.
How to work it
Insert the right needle into the front of the next stitch and knit it as normal, but instead of dropping the original stitch off the left needle, leave it there. Insert the right needle into the back loop of that same, still-live stitch and knit again. Only now slide the original stitch off the left needle — you've made two stitches from one.
The small bar it leaves, and where that matters
Unlike a yarn over's open hole, kfb leaves a small horizontal bar of yarn at the base of the new stitch — visible but not a hole, a genuinely different look from lace-style increases. For most plain fabric this bar is a minor, often unnoticed detail; for a project where a perfectly smooth, invisible increase matters (a fitted garment's side shaping, for instance), an M1 increase is generally preferred instead, since it leaves less visible trace than kfb's small bar.
Why kfb is still a popular default despite the bar
Kfb is mechanically simpler and faster to work than M1's lifted-strand technique, and doesn't require picking up a strand from the row below — for a project where the small bar isn't a real visual concern, or is even a slightly textured, intentional-looking detail, kfb's speed and simplicity make it a common default increase.
Where it shows up
Toe-up sock toes, mitten thumb gussets, and any pattern favoring a fast, simple increase over an invisible one all commonly specify kfb by name.
Related abbreviations
- m1 — a lifted-strand increase leaving less visible trace than kfb
- yo — a deliberately hole-leaving increase, used for lace rather than plain shaping
FAQ
Does kfb work on a purl row as well as a knit row? Yes — a purl-front-and-back (pfb) equivalent exists, following the same into-the-stitch-twice logic worked with purl motions instead of knit ones, for shaping on a wrong-side row.
Is kfb's visible bar always on the same side of the stitch? Yes, consistently — the bar sits at the base of the newly created stitch, on the side corresponding to the back-loop insertion, which is why kfb increases worked consistently down one edge of a piece produce a small but regular decorative line some patterns use deliberately.