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How to: Piece Diagonal Blocks and Rows

Quilt tops with blocks set diagonally, or on point, can be a bit more challenging to piece than straight-set blocks. Follow these tips for smooth sewing!

  • Cutting Setting and Corner Setting Triangles

    Featured Quilt: Red Double X (buy the pattern here)

    Because you are sewing in diagonal rows, you may have a greater tendency to stretch or distort the quilt blocks as you piece them together.

    It is essential to cut side setting triangles and corner setting triangles so the straight grain edge will be along the outer edges of the quilt. This will help prevent your quilt from becoming distorted or sagging.

    Note: Some quilters prefer to cut their side and corner setting triangles 1⁄2" to 1" larger than required and trim away the excess fabric after piecing the top.

    BONUS! Download our handy guide for cutting setting squares and triangles here.

  • Arrange Blocks and Setting Squares

    Lay out blocks and setting squares in diagonal rows. If you are including sashing between blocks, lay out the sashing pieces now, too.


  • Add Setting Triangles

    Add the side setting triangles and corner setting triangles to the layout.


  • Join Blocks

    With right sides together and raw edges aligned, join together the blocks (or blocks and sashing pieces) in each row. Sew the setting triangles to the ends of each row. Do not add the corner triangles.

    TIP: Seams don’t match? Did you square up your blocks? If so and the blocks still don’t line up in rows the way you’d like, take the time to remove stitching and rejoin blocks until the seams do match.


  • Press Seams

    Press seams to one side, pressing each row in alternate directions. For example, press the seams in row 1 and all odd-numbered rows to the right, and press seams in row 2 and all even-numbered rows to the left. Then when you assemble the rows, the alternated seams will nest together, ensuring matching seams.


  • Match the Seam Intersections

    Pin together rows 1 and 2, taking care to match seam intersections. You may need to ease the blocks a slight bit to ensure that the raw edges align. If one row is significantly shorter or longer, check your seam allowances to see if one is too narrow or too deep.

    If so, remove the seam and restitch it before joining the rows. Sew the rows together, backstitching at the beginning and end to secure the seam line and stabilize the quilt edge. Trim any threads and/or dog-ears.

    Continue joining rows in pairs (for example, join row 3 to row 4, row 5 to row 6, and so forth). Then sew together the joined rows. Press all seam allowances in the same direction.

    TIP: If you’re having difficulty aligning seams when sewing rows together, try sewing with the seam allowances on top facing away from you as you guide the rows under the presser foot. This forces the top seam to butt up to the lower seam so the two automatically lock together.

    TIP: Some quilters like to alternate the sewing direction of their rows when assembling a quilt center. If you tend to pull on your rows of blocks as you stitch them together and notice any distortion in the finished quilt top, try stitching one row left to right, the next right to left.

  • Stitch Corner Triangles

    Sew the corner setting triangles to the pieced rows to complete the quilt center (the 1⁄4" seam allowances of the corner triangles will extend beyond the edge of the quilt center). Trim any threads and dog-ears. Press seams toward corner setting triangles.

    Note: If you chose to cut your side and corner triangles larger than specified, you will need to trim them now, leaving a 1⁄4" seam allowance outside the corners of the pieced blocks.