High Round Back Adjuster
A horizontal fold across the upper back means the pattern needs more length there. Measure the fold and get the exact slash-and-spread adjustment.
Put the garment on wrong-side-out. Pinch out the horizontal fold at your upper back. Measure the depth of the fold (just one layer — not the doubled amount).
Measure from the neckline seam down to where the fold forms across your back.
Identifying a high round back
A high round back (also called a rounded upper back or kyphosis) causes the upper back to curve more than the pattern assumes. On a garment, this appears as a horizontal fold or ridge of excess fabric running across the back, below the collar and above the shoulder blades.
The fold is excess fabric — it means the pattern has too much ease in the upper back vertically. The adjustment adds length at that point, allowing the back to curve without pulling the hemline up or straining the neckline.
Don't confuse this with a full upper back (horizontal pulling and tightness, not a fold) or a swayback (horizontal fold at the lower back waist). Each requires a different adjustment.
How to measure the fold
Put the garment on inside out. Have someone pinch the fold flat so it lies smooth against your back. Measure the depth of the fold with a ruler — just one layer, not both sides doubled. This is your adjustment amount.
Also measure from the neckline seam to where the fold sits — this tells you where to place the slash line on the pattern.