A slit is a vertical opening sewn closed at the top, then left open below

A slit in a dress is an opening that runs vertically up the side seam, back seam, or front of the skirt. The opening itself is not sewn shut — instead, you sew the edges of the opening so they don't fray, then reinforce the top where the slit begins so it doesn't tear when you wear and move in the dress. The slit stays open from that reinforced point downward.

The most common slit is a side seam slit, which runs up the side of the dress from the hem. You can also sew a slit into a back seam or create one by cutting into a finished dress panel. The technique is the same regardless of location: finish the raw edges, reinforce the top, and leave the rest open.

Key Takeaways

  • A slit requires you to finish the raw edges with a serger, zigzag stitch, or binding so they do not fray when the dress is worn and washed.
  • The top of the slit must be reinforced with a bar tack or triangle stitch to prevent the opening from tearing upward into the seam.
  • A side seam slit is easiest to sew because you work with an existing seam line rather than cutting into a flat panel.
  • You can sew a slit into a dress before or after hemming, but finishing the edges before hemming prevents fraying at the hem edge.

Measure and mark where the slit will start and end

Decide how long the slit should be. A modest slit on a knee-length dress might be 6 to 8 inches; a floor-length gown might have a slit 12 to 18 inches long. Mark the top of the slit with a pin or tailor's chalk on the seam line where you want the opening to begin. Mark the bottom of the slit the same way.

If you are working with a side seam, the slit runs along the existing seam line. If you are cutting a slit into a back panel or front panel, use a ruler and chalk to draw a straight line from top to bottom, centered on where you want the opening. The line should be at least 1/2 inch from any edge so you have room to finish the raw edges.

Cut the slit if you are not using an existing seam

If the slit will run along a side seam that is already sewn, skip this step. If you are creating a new slit by cutting into a panel, use sharp fabric scissors to cut straight down the line you marked, stopping exactly at the bottom mark. Do not cut past it — the fabric below that point stays intact.

Cut slowly and use a ruler as a guide if you are nervous. Once you cut, you cannot undo it, so take your time. If you are cutting into a delicate fabric like silk or chiffon, place a piece of tissue paper under the fabric while you cut to prevent snagging.

Finish the raw edges with a serger, zigzag stitch, or binding

The two cut edges of the slit opening need to be finished so they do not fray. You have three main options: a serger, a zigzag stitch on a regular sewing machine, or bias binding sewn by hand or machine.

If you own a serger, thread it and run both edges of the slit through it. A serger cuts and finishes the edge in one pass, which is the fastest method. If you do not have a serger, set your regular sewing machine to a zigzag stitch (width 2.5 to 3, length 2 to 2.5) and sew along each edge of the slit, about 1/4 inch from the cut edge. The zigzag stitch locks the fibers and prevents fraying.

For a more finished look, especially on dressy fabrics, use bias binding. Cut or purchase 1/2-inch bias tape. Fold it in half lengthwise and press it. Slip one edge of the slit into the fold of the bias tape and pin it. Sew the binding down with a straight stitch, sewing through all layers. Fold the binding to the back side and hand-stitch or machine-stitch it down. This method takes longer but creates a polished edge.

Reinforce the top of the slit with a bar tack or triangle stitch

The top of the slit — the point where the opening begins — is under stress every time you move. Without reinforcement, the opening will tear upward into the seam. You must reinforce this point before wearing the dress.

The easiest method is a bar tack: a short line of tight stitches sewn perpendicular to the slit. Set your machine to a straight stitch and sew back and forth across the top of the slit opening, about 1/4 inch wide and 1/2 inch long. Sew 4 to 6 passes, then tie off the thread. The bar tack looks like a small rectangle of stitches and holds the fabric together at that critical point.

Alternatively, sew a small triangle: start at one corner of the slit top, sew diagonally to the opposite corner, then sew back along the other diagonal to form a triangle. This distributes the stress over a slightly larger area. Either method works — choose whichever you find easier to execute.

Press the slit edges flat and hem the dress

Once the edges are finished and the top is reinforced, press the slit flat with an iron. If you finished the edges with a zigzag stitch, press them to one side — usually toward the back of the dress or toward the center. If you used bias binding, press it flat against the dress.

Now hem the dress if you have not already. The hem should run all the way to the bottom of the slit opening. When you sew the hem, the stitches will anchor the finished edges of the slit and prevent them from rolling or curling during wear and washing.

Frequently Asked Questions

Can I sew a slit into a dress that is already finished?

Yes. Mark where you want the slit, cut it carefully, finish both edges with a zigzag stitch or binding, and reinforce the top with a bar tack. The only difference is that you will be working around an existing hem, so you may need to carefully unpick a few stitches at the hem edge to finish the slit edges neatly.

What if the slit is on a side seam that is not yet sewn?

Sew the seam as normal, but stop at the mark where the slit begins. Backstitch to find the thread. Leave the seam open below that point — do not sew it closed. Then finish the raw edges of the open seam and reinforce the top where you stopped sewing.

How do I prevent the slit from tearing if I make it too long?

A longer slit needs a stronger reinforcement at the top. Use a triangle stitch instead of a bar tack, or sew two bar tacks stacked on top of each other. You can also add a small piece of interfacing behind the top of the slit before reinforcing it — this adds stability to that stress point.

Should I finish the slit edges before or after hemming the dress?

Finishing before hemming is easier because you can access both edges of the slit opening without working around a finished hem. However, you can do it either way. If you hem first, you will need to carefully work around the hem stitches when you finish the slit edges.