How to Sew Single Welt Pockets: A Step-by-Step Tutorial

A welt pocket is the slot-style pocket you see in tailored garments — a narrow horizontal opening with a fabric strip (“welt”) covering the bottom edge, and the pocket bag itself hidden inside the garment. Once you understand how a welt pocket is constructed, the related variations — double welt pockets, welts with flaps, jetted pockets — are all small modifications of the same technique.

This tutorial covers the single welt pocket, the simplest form. It’s the most-used welt style on shirt chest pockets, blazer breast pockets, and some trouser back pockets. Master this, and the others follow easily.

What a single welt pocket looks like

From the outside: a narrow horizontal slit, with a fabric strip about 1.5–2 cm wide running along the bottom edge of the slit. The slit opens into a pocket inside the garment.

From the inside: a fabric pocket bag attached to the back of the welt and to the edges of the slit, hidden behind the garment fabric.

Geometric components:

Welt fabric: the visible strip on the outside.
Pocket bag (top): extends upward from the slit’s top edge.
Pocket bag (bottom): extends downward from the welt and connects to the top of the pocket bag inside the garment.

These are sewn into a precise rectangular opening cut through the garment fabric, with the welt covering the bottom edge of the opening.

When to use a welt pocket

Tailored garments: blazers, suits, dress shirts, formalwear.
Trousers: traditional dress trouser back pockets often use a welt or double-welt design.
Modern casual wear: trench coats, peacoats, sometimes structured jackets.

Welt pockets aren’t the right choice for casual wear (T-shirts, sweatshirts) or for projects where the pocket needs to hold heavy items (welt pockets are decorative and shallow; in-seam or patch pockets carry weight better).

What you need

The garment piece where the welt pocket will be installed.
Welt fabric: a small strip about 4 cm × 16 cm (longer than the welt opening). Same fabric as the garment for blending, or contrast for design.
Pocket bag fabric: lightweight cotton or pocketing fabric in the same colour as the garment. Two pieces, each about 18 × 16 cm.
Fusible interfacing: a small piece, same dimensions as the welt — applied to the welt for stiffness and structure.
Fabric marker, ruler, sharp scissors or seam ripper, sewing machine, thread, iron.

Step 1: Mark the welt position

On the right side of the garment fabric, mark the exact position of the welt opening with a fabric marker:

A horizontal line where the welt opening will be (the slit).
The two ends of this line, marking the welt’s full width (typically 11–13 cm wide).
A second horizontal line about 1.5 cm below the first, marking the bottom edge of the welt.

Mark the welt as a precise rectangle: two parallel horizontal lines 1.5 cm apart, with vertical end markers defining the welt's width.

The rectangle defined by these two horizontal lines is where the welt will sit visibly on the garment. Mark precisely — small inaccuracies show.

Step 2: Prepare the welt

Cut the welt fabric to size: 4 cm × 16 cm.
Apply fusible interfacing to one half (the top half lengthwise). The interfaced half becomes the visible welt; the un-interfaced half becomes the seam allowance hidden inside.
Fold the welt in half lengthwise, right side out, so the interfaced half is on top. Press.

The welt is now a folded strip about 2 cm wide and 16 cm long, with the interfaced layer on top.

Step 3: Pin the welt and pocket bag pieces

This step requires precision.

Place one piece of pocket bag fabric on the wrong side of the garment, with its top edge sitting at the bottom marked line of the welt position. The pocket bag extends downward into the garment interior.
Pin the pocket bag piece in place from the right side, with the pins going through both layers.

Now flip back to the right side:

Place the folded welt on the right side of the garment, aligned along the bottom marked line. The folded edge of the welt points downward; the raw edges (the un-interfaced strip) point upward into the welt slit area.
Pin the welt in place, with pins inside the welt area.

Finally, the second pocket bag piece:

Place the second pocket bag piece on the right side, sitting on top of the welt. Its top edge is just above the upper marked line.

The construction stack from bottom to top is now:

Garment fabric (right side up).
First pocket bag (on wrong side, behind garment, hanging downward).
Welt (folded, on right side of garment, between the two horizontal lines).
Second pocket bag (on right side of garment, on top, hanging upward).

Pin everything together.

Step 4: Sew the two long edges

This is the precision step.

Sew along the upper horizontal line, going through all layers. Stitch length about 2.0 mm. Sew from one marked end to the other — exactly between the marks. Backstitch at both ends, but not too aggressively (you don’t want to extend the stitching beyond the marks).
Sew along the lower horizontal line, going through all layers. Same precision — from one marked end to the other, backstitched at both ends but not extending past.

You now have two parallel rows of stitching, each precisely the length of the welt opening, on either side of the welt strip.

Step 5: Cut the slit

Now the moment of commitment: cutting the slit between the two rows of stitching.

The cuts form a Y-shape at each end. The diagonals must reach the very corners of the stitching — but not through them.

From the right side:

Use a sharp seam ripper or small scissors to cut between the two rows of stitching. Cut down the centre of the slit area, but stop about 1 cm short of each end.
At each end, cut diagonally toward the corners — toward the very ends of your stitched lines, but not through them. The diagonal cuts let the welt opening open up cleanly without the corners pulling.

The cuts form a long horizontal slit with small triangular flaps at each end.

Step 6: Push the components through

Push the welt strip down through the slit to the wrong side of the garment.
Push the upper pocket bag piece (the one on top) down through the slit to the wrong side.

When done, the welt sits on the right side of the garment (with the folded edge along the bottom of the slit), and the pocket bag pieces are on the wrong side ready to be assembled into a pocket.

Step 7: Press the slit edges

From the right side:

Press the welt flat, with the folded edge along the bottom of the slit.
Press the slit’s top edge upward (away from the welt) for a clean welt boundary.

The welt should now look finished from the right side.

Step 8: Sew the small triangles at each end

The diagonal cuts at the slit ends produced small triangular flaps. From the wrong side:

Push the triangles to the wrong side, so they hide behind the welt.
With the welt out of the way, sew a small reinforcement stitch at each end of the slit, securing the triangle to the welt and the slit edges. Stitch back and forth a few times to lock in place.

This is what holds the welt opening from coming apart when the pocket is used.

Step 9: Sew the pocket bag

Now the pocket bag itself:

From the wrong side, find the two pocket bag pieces hanging from the slit edges.
Pin them together along the bottom and side edges (don’t pin the top, where the bag attaches to the slit).
Sew with a 1 cm seam allowance from one side, around the bottom, and up the other side.
Trim corners and any excess seam allowance.

The pocket bag is now a closed bag attached to the welt opening, hidden behind the garment fabric.

Step 10: Final pressing and check

Press the welt flat from the right side. Check:

The welt opens with a clean slit that doesn’t pull at the corners.
The pocket bag is fully hidden when the welt is closed.
No raw edges show.
The welt sits flat against the garment, not popping up.

Common welt pocket mistakes

The welt opening is uneven

Stitching wasn’t precise. The two horizontal lines weren’t sewn at exactly the same length, or one line strayed off the marked position. Re-do, paying special attention to start and stop points.

The corners ripped or frayed

The diagonal cut at the corners went through the stitching. Re-do, being more careful with the cut depth.

The welt is the wrong width

Your welt fabric was cut wrong, or the spacing between the two horizontal stitching lines was wrong. The width of the visible welt should match the gap between the lines.

The welt opens with a gap (showing the inside)

The triangles at the ends weren’t pulled fully through to the wrong side, or weren’t reinforced. Re-pull and re-stitch the ends.

The pocket bag is too small to be useful

Pocket bag pieces too small. Use 18 × 16 cm pieces minimum, larger for trousers (24 × 22 cm). The pocket bag should be roughly twice as long as wide.

The pocket bag bunches inside the garment

Pocket bag pieces aren’t pressed flat against the garment back. After assembly, press carefully from the inside.

Variations on the basic technique

Once you’ve made a single welt:

Double welt pocket

Two welts (instead of one) cover the slit — one on top, one on bottom, with a narrow gap between. The construction is similar but uses two welt strips instead of one. The result is a more refined pocket, common on trouser back pockets and blazer hip pockets.

Welt with flap

A single welt with an additional fabric flap covering the slit. The flap is sewn into the upper edge of the slit and falls down to cover the welt. Common on jacket pockets and trousers.

Jetted pocket

A welt-style pocket with no visible welt — the slit is bound with two narrow strips of fabric (welts) but neither protrudes. Used for high-end tailoring.

Each variation is a small modification of the basic single welt construction. Master the single welt and the others become approachable.

Practising on scrap

Critical: practise welt pockets on scrap before committing to a garment. The technique requires precision that improves with repetition.

Cut two 30 × 25 cm pieces of cheap cotton (one to be the “garment,” one for the pocket bag).
Cut a welt strip and pocket bag pieces.
Walk through the steps above, paying attention to where mistakes happen.

The first welt is rough. The second is much better. By the fifth practice welt, you’re confident enough to do it on real fabric.

What welt pockets unlock

Once you can make welt pockets, you can sew:

Tailored trousers with proper back pockets.
Blazers with breast and hip welt pockets.
Coats with horizontal slot pockets.
Dress shirts with welt chest pockets.
Lined jackets with both welt pockets and lining.

Combined with the other intermediate techniques — invisible zippers, lining, set-in sleeves — welt pockets are part of the toolkit that makes tailored garment construction possible.

Closing thought

Welt pockets are intimidating because they look complex from the outside. The actual construction is just precise rectangular sewing — straight lines, careful cuts, no curves. What separates good welts from bad welts is precision rather than skill: marking carefully, sewing exactly to the marks, cutting the diagonal corners exactly to the stitching ends.

Once you’ve made a few practice welts on scrap and one real welt on a garment, the technique demystifies. Subsequent welts are routine — pleasant to make, satisfying to finish, and dramatically improve the appearance of any garment you sew them into.

For where welt pockets fit in the broader intermediate-skills journey, see our complete intermediate techniques roadmap. For the next step beyond intermediate, see our advanced tailoring roadmap.