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Quilting How-To: Quarter Square Triangle

Quarter square triangles are building blocks for many more complex blocks.  It can also be used in borders and by itself to make many amazing designs.

There are many ways to make Quarter Square Triangles.  I find the following method to be the easiest and most accurate.  This method makes 4 identical blocks.

  • Cut 1 square of fabric for each of the four colors used in the quarter square triangle.  For the example picture you would cut 2 blue squares, 1 red and 1 white.
  • Determine the minimum size of the squares by taking your desired finished square size and adding 1 1/4 inches to it.  For example if you want a 6 inch finished square then cut 2 blue, 1 red, and 1 white square at least 7 1/4 inches. 

  • Cutting your squares a little larger than necessary makes everything easier and allows you to be more accurate.  For a 6 inch finished square I usually cut my starting squares 7 1/5 inches instead of 7 1/4.

  • Make two stacks of two squares right sides together.  The stack should be colors that touch on a long edge.  In the example stack a blue with red and a blue with white.  You would NOT stack the red with the white.

  • Mark diagonal and sew a scant 1/4 inch seam on both sides of marked line.  If you make your squares oversized you have to be less worried about the "scantness" of your 1/4 inch seam.

  • Cut on marked line to create 2 half square triangles.  Press seam toward the darker fabric or press the seam open.

  • Stack half square triangles from the previous step right sides together aligning the seams. Insure that the orientation is correct.  In our example, we stack each blue and white block with a red and white block.  The white triangles are opposite each other.

  • Mark diagonal. Sew a scant 1/4 seam on each side of the diagonal.

  • Cut on diagonal, press seam open.

  • Square up the patches to the finished size plus 1/2. For example for a 6 inch finished square trim to 6 1/2 inches.

  • To square up the block, a square ruler the exact size of the square is very useful.  A larger square ruler may also be used.  The ruler must have at least one 45 degree line.

  •   Align the 45 degree line with one of the diagonal seam on the block. The center point of the block should be exactly middle of the block.  So for our 6 1/2 block the center should be at 3 1/4 from the edges.  After placing the ruler in the correct position and double checking it....trim the edges to the proper size. 

  • In necessary, turn the block and re-position the ruler to trim the remaining sides.

  • If you made the starting squares a little over sized, there will be more waste at this point.  However, there is less chance that the quarter square triangle will be too small!

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