Henry Ernest Dudeney/Modern Puzzles/117 - The Patchwork Quilt/Solution

Modern Puzzles by Henry Ernest Dudeney: $117$

Here is a patchwork quilt that was produced by two young ladies for some charitable purpose.

When they came to join their work it was found that each lady had contributed a portion that was exactly the same size and shape.

It is an amusing puzzle to discover just where these two portions are joined together.

Can you divide the quilt into two parts, simply by cutting the stitches, so that the portions shall be of the same size and shape?

Except for my warning the reader might have supposed that the dark zigzag line from $A$ to $B$ would solve the puzzle.

But it will not, because the pieces are not of the same size and shape.

It would be all right if we could go along the dotted line $D$ instead of $C$, but that would mean cutting a piece.

We must cut out all the shaded portion on one piece, which will exactly match the other.

One portion of the patchwork is drawn in just to guide the eye when comparing with the original.