In sewing, a tapering tuck, used to fit fabric, which is flat, over a curved surface. The dart goes into an otherwise unsewn area, as opposed to being part of a seam. Most tailored garmets have them.

On a pattern, a dart is marked as follows:
          ·
         /|\
        / | \
       /  |  \
    A ·   |   · B
       \  |  /
        \ | /
         \|/
          ·

To sew the dart, fold the fabric along the vertical line so that dot A and dot B match up. Then stitch along the diagonal lines. Open the fabric up and press it as flat as it will go.

Darts are also used to narrow fabric at an edge, for instance, to fit trousers in the seat. In that case, the dart is marked as follows.

  A       B
__.___.___.__ 
---\--|--/--- <- seam allowance marking
    \ | /
     \|/
      ·

This dart is sewn in the same way as the dart in the middle of a garment.

Deep darts can create not just a concavity in the garment (useful for waistlines), but a distinct pointed effect.