How to Knit a Vertical Buttonhole
A vertical buttonhole is stretchier than a cast-off horizontal buttonhole. You work each side of the vertical buttonhole with a separate ball of yarn. Test the buttonhole opening with the width of your button to know how many rows to work to achieve an accurately sized buttonhole.
A vertical buttonhole is often worked in 1x1 ribbing and 2x2 ribbing. When worked in a rib, a vertical buttonhole is easily camouflaged in the purl trough. However, this style of buttonhole can also be worked in seed stitch and garter stitch, both of which create a nice clean edge for the buttonhole.
Row 1: RS: Work in 1 x 1 rib pattern to the position of the buttonhole.
End with a knit stitch, ready to work a purl stitch. The purl stitch should be in the center of the buttonband.
Purl into the front and the back of the next (purl) stitch.
Increasing 1 stitch in the purl trough allows for each side of the buttonhole to be edged by a purl stitch on the RS. If you're working in a 2x2 rib, garter stitch, or seed stitch, no increase is needed.
Continue in the rib pattern to the end of the row.
Work in 1x1 rib to the end of the buttonband or row. If you're placing this vertical buttonhole in a garment you'll need to work in 1x1 rib to the end of the buttonband and then in the garment pattern to the end of the row.
Row 2: WS: Work in 1x1 rib to increased stitch. You'll notice two knit stitches (this is where you have increased) with a purl stitch on either side. Note: If you're placing this vertical buttonhole in a garment you will need to work in garment pattern until you reach the buttonband. Work in 1x1 ribbing until you have reached the increased stitch.
Work Row 2 in the rib pattern to the increased stitch.
There will be two knit stitches with a purl stitch on either side.
Knit the increased stitch.
The increased stitch is the first of the two knit stitches.
Attach a second ball of yarn, knit the second knit stitch, and then work in 1x1 rib (or stitch of choice) to the end of the row.
Begin with k1.
Row 3: RS: Work in 1x1 rib to the where the first ball of yarn is attached.
Use first ball of yarn to complete 1x1 row. Note: If you're placing this vertical buttonhole in a garment you'll work in garment pattern to the end of the row.
Repeat Rows 2 and 3 as many times as needed for the right size buttonhole.
Close the buttonhole.
On a RS row, purl the 2 stitches at the top of the hole together. On a WS row, knit the 2 stitches at the top of the hole together.
To finish, cut the separate strand and weave in the ends.
Weaving the ends in along the edges of the buttonhole helps keep it from stretching.