How to Sew Finished Cape Openings Into a Costume Suit

A faced opening has a fabric patch sewn around its perimeter and turned inside, enclosing the cut edges. A bound opening adds folded fabric lips that meet across the opening. Threads demonstrates faced windows as the first stage of shaped buttonholes, while Seamwork explains how welts fill or frame an opening. Both constructions can inform a costume detail. Unconventional Buttonholes, Conquering the Welt

Use the faced window described below when a cape tab needs a small amount of clearance through the suit. Choose a bound finish instead if your design calls for an opening that looks closed when the cape is removed. Do not add welt lips to the measurements below without making another sample: the folds change the available passage.

Start with a stable woven fabric and a lightweight facing. For sheer or delicate costume fabric, reconsider the construction after sampling: Janome specifically notes that bound-buttonhole patches can show through or add unwanted bulk in those materials. A fitted stretch suit also needs a separate construction trial because the reinforced area must work with the surrounding stretch. CONTINENTAL M6 Instruction Book, printed pages 64–65

Finish the cape tabs before sizing their openings. Include any folded edges, lining and seams that will actually pass through the suit. A measurement taken from an unfinished strip will not represent the finished tab’s thickness.

Baste the suit together sufficiently to establish its finished shape, then position the cape and mark where each tab should emerge. Check the route on the inside as well as the outside. Keep the proposed windows clear of the zipper, bulky seam intersections and decorative layers that would obstruct turning the facing.

For a pair, record each opening’s distance from the same construction reference, such as the center-back seam and a horizontal pattern line. Compare the marks with the cape in position before assuming that equal distances alone give the intended appearance. If altering a completed lined suit, open enough lining seam to reach the shell and keep the layers separate while sewing.

Use a sample to determine both the opening’s length and its short dimension. Length accommodates the tab’s width; the short dimension provides room for its thickness and the way it enters the suit. The following dimensions are illustrative starting points, not a universal cape-opening specification.

Sample component	Illustrative measurement
Finished cape tab	40 mm wide
Finished rectangular window	50 mm long × 8 mm high
Facing patch	100 mm × 60 mm
Reinforcement patch	Large enough to extend beyond the window on every side

Here, the length allowance is 50 − 40 = 10 mm, or approximately 5 mm at each end when the tab is centered. The proposed 8 mm height still needs testing with the actual tab. Thread it through the completed sample at its intended angle; increase or decrease the window dimensions before marking the suit.

Make the sample from the same shell, reinforcement and facing combination you intend to use. Include lining if the suit has it. This turns the sample into a useful construction check: you can assess clearance, visible patch outlines and pressing response together.

Gather matching thread, a ruler, removable marking tools, small sharp scissors, a hand-sewing needle and pressing equipment suitable for the fabric. Cut one facing patch per opening, keeping its grain aligned with the shell for this rectangular version.

Apply suitable interfacing to the shell’s wrong side around each opening, following the interfacing manufacturer’s application instructions. First test its appearance on your sample. Seamwork identifies interfacing as a way to reduce fraying around a welt opening and emphasizes stabilization when an opening runs diagonally. Conquering the Welt

Finish the facing patch’s outer edges with a narrow zigzag or overlocking stitch without stretching them. Draw the finished window rectangle on the facing’s wrong side. Center the facing over the marked location, right sides together, and baste outside the rectangle. Keep the lining completely out of this seam.

Sew exactly around the marked rectangle. At each corner, stop with the needle down, lift the presser foot, pivot and continue. Threads’ original window-opening tutorial uses a 1.5 mm stitch length and overlaps the beginning stitches rather than backstitching to limit bulk; test that setting on your fabric combination first. Decorative pockets or bound buttonholes

Inspect the stitching from both sides before cutting. The long edges should be parallel, and every corner should be fully stitched. Correct a wandering line now, while the fabric remains intact.

Cut through the facing and shell along the rectangle’s center, stopping short of each end. Make diagonal cuts from the center slit toward the four stitched corners, leaving a small triangular allowance at each short end. Clip close enough for the corners to turn, without cutting the stitches. Accurate corner clipping is central to the corresponding welt construction described by David Page Coffin. Conquering the Welt

Push the facing through the slit to the suit’s wrong side. Gently arrange the four corners and roll the seam slightly inward so the facing does not show on the outside. Press using the settings established on your sample. Turning a stitched window facing to the wrong side and pressing it is the underlying technique demonstrated in Threads’ faced-buttonhole instructions. Unconventional Buttonholes

Baste around the window to hold its shape. For this costume adaptation, a narrow line of visible topstitching is one practical way to keep the facing from rolling out: test the appearance first, then stitch evenly around the perimeter, catching the facing beneath. Keep the opening unobstructed.

Secure the facing’s outer edges with small hand stitches to nearby seam allowances where available. Avoid pulling those stitches tight enough to distort the shell. Pass the cape tab through again before proceeding to the lining.

Let the lining settle into its normal position inside the suit. Transfer the opening’s four corners to it rather than relying solely on the original pattern marks. Janome’s bound-buttonhole instructions use corner pins to transfer the opening to a garment facing, then turn its cut allowances inward and hand-sew the perimeter. CONTINENTAL M6 Instruction Book, printed page 65

For this faced-window adaptation, separate the lining from the shell again and sew a small lightweight facing patch around the transferred rectangle. Cut, clip and turn that patch as you did for the shell. Return the lining to position and slipstitch its finished window to the shell facing around the passage, keeping the stitches off the suit’s exterior.

Leave the surrounding lining relaxed. If bringing the two windows together creates diagonal folds, release the basting and check their alignment before sewing permanently. Close the lining access seam only after the cape tab passes through cleanly.

Use these checks to decide what to adjust. They are practical applications of the construction sequence, rather than measured performance claims.

What you see	What to check next
A corner forms a small tuck	Check whether the diagonal clip reaches close enough to the stitched corner; do not snip blindly.
Facing shows outside	Re-roll the seam inward, baste and press before securing it.
Tab catches inside	Look for exposed allowances, a twisted facing or a lining window that is offset.
Fabric ripples around the window	Compare the sample before and after reinforcement and stitching to identify the stage introducing distortion.
Reinforcement outline is visible	Try a lighter compatible reinforcement on another sample before altering the suit.

Bound openings need their own checks if you choose that alternative. Johanna Lundström’s construction tutorial shows separate folded welt strips and secures the clipped end triangles to them; those steps belong to a bound finish and should not be omitted when adding lips. How to sew bound buttonholes

Complete one sample with the actual cape tab before sewing the pair into the suit. Once its clearance, corners and inside finish work together, repeat the same measurements and layer order for both openings, then check them with the cape attached and the suit arranged as it will be worn.

• Unconventional Buttonholes — Threads
• Conquering the Welt — Seamwork
• Decorative pockets or bound buttonholes — Threads
• CONTINENTAL M6 Instruction Book — Janome
• How to sew bound buttonholes — The Last Stitch