How to make a shoulder bag (flap)

1. Materials & tools

Materials (a standard-size bag)

• Outer fabric (canvas, denim, faux leather) — about 40 × 90 cm (16 × 35 in)
• Lining (cotton, quilting) — the same amount
• Fusible interfacing (on the outer keeps the shape) — the same amount
• Strap webbing (about 2.5 cm wide cotton or nylon tape) — about 120 cm, adjustable
• 1 swivel hook and 1 rectangle ring
• 1 magnetic or metal snap for the flap

Tools

• Sewing machine (or needle and thread)
• Fabric marker or pencil
• Ruler and scissors
• Iron
• Pins or clips

2. Make the pattern (auto-generated in Katagami)

With the Katagami pattern tool, you just enter the finished size and it drafts a seam-allowance-included pattern, tiled to print at actual size on Letter or A4.

1. Open the tool
   Open the pattern tool and choose “Bags” → “Shoulder bag” from the tabs at the top.
2. Enter the size
   Enter the width, height, flap depth, strap length and strap width, or pick a mini / standard / A4 preset. The pattern gives body, flap and strap pieces.
3. Set the seam allowance
   Use the slider at the bottom (beginners: 1.0–1.5 cm / about 3/8–5/8 in).
4. Print
   Press “Print (actual size)”, then in the print dialog set Scale = 100% and turn “Fit to page” OFF. Check the 50 mm calibration box on the first guide sheet with a ruler.

3. Cutting the fabric

1. Cut the body
   Cut 2 outer and 2 lining body pieces (4 total) for front and back.
2. Cut the flap
   Cut one outer and one lining flap.
3. Cut the strap
   Cut one strap piece, or cut ready-made webbing to length.
4. Interface
   Fuse interfacing to the wrong side of the outer body and flap and press.

4. Sewing

4-1. Make the flap

1. Place the flap outer and lining right sides together and sew around, leaving a 5–6 cm turning gap on the top edge.
2. Clip the corners and curves, turn right side out, and close the gap with a slip or edge stitch.
3. Fit the female snap centred and slightly low on the flap lining.

4-2. Make the body

1. Place the front and back outer pieces right sides together and sew the bottom and both sides; round the corners if you like.
2. Sew the lining the same way, leaving about a 10 cm gap in the bottom seam.
3. Turn the outer right side out and fit the male snap on the front, where the flap lands.

4-3. Prepare the strap

1. Fold the strap fabric right sides together along the long edge, sew, and turn right side out (skip for ready-made webbing).
2. Thread each end through the swivel hook and rectangle ring, fold back and stitch to secure.

4-4. Finish

1. Catch the strap ends (or D-rings) at the top of each side seam of the outer.
2. Slip the lining inside the outer and sew them together around the opening.
3. Pull everything right side out through the gap in the lining and close the gap.
4. Sew the flap to the top of the back opening to finish.

5. Tips & variations

• Add a gusset: sew a triangle at each bottom corner for a boxed base — 4–6 cm gives a roomy, stand-up shape.
• Inner pocket: a zip or slip pocket on the lining front makes it far more practical.
• Adjustable strap: add a slide buckle with the rectangle ring for a two-way shoulder/crossbody length.