In wrap skirts, dresses, or double-breasted jackets, the underwrap is the interior panel that crosses over the body first and is covered by the outer layer. It must be cut wide enough to prevent exposing the wearer when moving or sitting. Designers often secure the underwrap with an internal button, tie, or snap to maintain the garment's structural alignment.
Heard on the job
Add a hidden buttonhole to the underwrap so the skirt doesn't blow open when she walks down the runway.