Quick Answer

The Double T quilt block combines half-square triangles and squares to create a classic interlocking design. This tutorial walks you through the piecing steps and common pitfalls so you can sew it with confidence.

Why the Double T Block Works for All Skill Levels

The Double T block is a traditional pattern that looks more complex than it is. Its structure relies on simple units: squares and half-square triangles arranged in a nine-patch grid. This makes it approachable for beginners while offering enough variety to keep experienced quilters engaged.

One trade-off: the block requires precise seam allowances to keep the T shapes crisp. If your 1/4-inch seam drifts, the arms of the T can become uneven. Pressing seams toward the darker fabric also helps reduce bulk where units meet.

Using the Let's Stitch A Year of Blocks Course

The Let's Stitch A Year of Blocks: Double T course from Piece N Quilt provides step-by-step video instruction for this block and eleven others. Natalia demonstrates both free-motion quilting and ruler quilting techniques, so you can practice different methods on the same block design.

Because the course covers an entire year of blocks, you can build skills progressively. Each block introduces new quilting motifs, from feathers to geometric fills, without overwhelming you. The Double T block is a great starting point because its open areas give you room to try different stitch patterns.

How to Sew the Double T Quilt Block

  1. Cut your fabric pieces: For one 12-inch finished Double T block, cut: one 4.5-inch square for the center T intersection (background fabric), four 4.5-inch squares for the T arms (accent fabric), and four 4.5-inch squares for the corners (background fabric). You will also need four 5-inch squares of accent fabric and four 5-inch squares of background fabric to make half-square triangles. Common mistake: cutting all squares the same size. The half-square triangle units require slightly larger squares (5 inches) so you can trim them to 4.5 inches after sewing.
  2. Make the half-square triangles: Pair each 5-inch accent square with a 5-inch background square, right sides together. Draw a diagonal line on the lighter fabric, then stitch 1/4 inch on each side of the line. Cut along the drawn line, press open, and trim each unit to 4.5 inches square. You will have eight half-square triangles. Checkpoint: press seams toward the darker fabric. If you press them open, the seams at the T intersections will be bulkier and harder to match.
  3. Arrange the block units: Lay out the nine 4.5-inch units in a three-by-three grid. Row 1 (top): half-square triangle (dark triangle pointing down-left), background square, half-square triangle (dark triangle pointing down-right). Row 2 (middle): background square, accent square (T arm), background square. Row 3 (bottom): half-square triangle (dark triangle pointing up-left), background square, half-square triangle (dark triangle pointing up-right). Common mistake: mixing up the orientation of the half-square triangles. The dark triangles should point toward the center of the block to form the T shape.
  4. Sew the rows together: Sew the three units in each row together with a 1/4-inch seam. Press seams in alternating directions: press row 1 seams to the left, row 2 to the right, and row 3 to the left. This helps seams nest when you join the rows. Checkpoint: after sewing each row, measure the row height. All three rows should be exactly 12.5 inches wide. If a row is narrower, your seam allowance may be off.
  5. Join the rows and press the block: Pin the rows together at the seam intersections, matching the nested seams. Sew the three rows together. Press the final block flat, pressing seams open or to one side as you prefer. The block should measure 12.5 inches square. Common mistake: not pinning at the seams. The T arms can shift, making the vertical line of the T look crooked. Always pin directly through the seam intersections.

Course That Teaches This Block

  • Let's Stitch A Year of Blocks: Double T: Clear step-by-step videos take the mystery out of free-motion quilting and ruler quilting. You can watch exactly how to quilt the Double T block, then practice alongside the video until you feel confident with each technique.

    Let's Stitch A Year of Blocks: Double T

    Let's Stitch A Year of Blocks: Double T