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What Is a Quarter Square Triangle Unit?
Learn how to make easy quick pieced quarter square triangle units without cutting and sewing individual triangles.
Quarter Square Triangle Unit Construction
Quarter square triangle units are square patchwork units that are made up of four equally-sized 90-degree triangles. The fabric's sturdy straight grain runs parallel to the longest side of each triangle, where it helps keep the outer edges of units from stretching as you work on a quilt.
Quarter square triangle units are used in the outer midpoints of each Ohio Star quilt block illustrated above. The traditional Card Trick quilt block is another popular quilt block that's made in part from quarter-square triangle units. The units can be assembled by sewing triangles together individually but quick piecing methods are easier, and usually more accurate.
Use Half Square Triangle Units as Parents
Half-square triangle units are used to make thousands of traditional patchwork quilt blocks. We'll put half-square triangle units to work again, using them as parents for the quarter-square triangle patchwork units.Continue to 2 of 3 below.
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Make One Type of Quarter-Square Triangle Unit
- Choose a finished size for your quarter-square triangle units or refer to the quilt pattern for the unit dimensions.
- Add 1-1/4" to the finished width and height and cut two contrasting squares to match the calculated size. If the finished size is 3" x 3", cut squares that measure 4-1/4" x 4-1/4".
- Use the quick pieced half square triangle unit method to sew the squares together, then cut apart and press as directed in the instructions to create two half-square triangle units.
- Turn one half-square triangle unit to its reverse side and draw a diagonal line from one corner to another—the line will flow across the seam.
- Align the two units right sides together, with contrasting triangles facing each other.
- Sew together with two seams, each 1/4" away from the drawn line, the same method used to create the parent units.
- Cut the squares apart on the line, press units open and trim away triangular nubs at the ends of the seam allowances.
- You'll have two quarter square triangle units that are 1/2" wider and taller than the finished size.
You can use any method to construct the parent half square triangle units. Try the Magic 8 technique if you're sewing lots of identical triangles. Alter cutting sizes if other methods are used.Continue to 3 of 3 below.
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Make Quarter Square Triangle Unit Variations
Change the appearance of quarter square triangle units by constructing them with varying combinations of parent squares:
- Top: When quarter-square triangle units are made from two identical half-square triangle parents, the resulting patchwork squares are identical and symmetrical.
- Middle: Substitute a plain square for one of the parents to make units with two quarter-square patches in one-half of the square and a single triangle in the other half. The units are mirror images of each other.
- Bottom: Use two different half-square triangle parents to make the quarter-square triangle units. The units are mirror images of each other but that doesn't usually matter if you're making a scrap quilt.
If some units cannot be used, weigh the advantages of quick piecing vs. sewing individual triangles together to create the patchwork you need. For instance, if we were making small quarter square triangle units, we would opt for the quick-pieced method simply because it eliminates the need to handle tiny triangles.
Throw extra units into a patchwork bin and use them later in another project.
If you decide to assemble quarter-square units from individual triangles, remember that the fabric's straight grain should be parallel to each triangle's longest edge.