Tips to Make Wizardry Semi Square Three Sided Blocks


A semi-square triangle (HST) is a patchwork square consisting of two right-angled triangles. Each triangle occupies exactly half of the inner area of the square. No matter what you call them, you’ll find that HST elements are among the most popular types of patchwork found in quilts, so it’s a good idea to explore more than one method of making them. You can stitch two right triangles together to make a square triangle, but the individual triangles stretch along their long oblique edges. Why bother if the methods of quick selection of fragments eliminate the need to mess with bias?

If all you need is two ready-made semi-square triangles, then the correct solution is the HST block assembly method. It’s easy and fast, and perfect for quilts. The magic 8 method is very similar, but it doubles the results by stitching the equivalent of four paired squares at the same time. With magic 8, making enough HST for a quilt like the Hunter’s Star is easier than ever.

Many years ago, many of us sewed HST products by attaching fabric to a mesh drawn or printed on paper, following the sewing lines before cutting the flaps into pieces. The magic 8 method is a simplified version of this technique. We will draw only a small section of the grid and draw the lines directly on the fabric, not on paper or other material.


Read all the instructions to get a general idea of how to prepare magic eight HSTS. Use any type of marker that does not soak into the fabric (or is not erased from it), if possible something with a sharp end.

Drawn grids are still popular and are now commercially available, although most of them are made of long strips rather than a large square or rectangle. Square meshes may be well suited for small HST blocks, but they become inconvenient when sewing larger patchwork. When applying the mesh directly to the fabric, the larger the mesh, the higher the probability of error.

What you will need
Equipment / Tools

Marking pens or pencil
Rulers for quilting
Rotating cutter and mat
Sewing machine customized for embroidery
Iron and ironing board


Cotton Fabric Trimmings for classes


Size determination

Your template should tell you the final size of the HST square units. The formula for calculating the size of two contrasting squares of fabric is as follows:
Multiply the finished size by 2.
Add 1-3/4 inches.

Cut two (contrasting) squares of fabric according to the calculated size. For your HST practice, let’s make 3 x 3 inch HST blocks.
3 inches x 2 = 6 inches
6 inches + 1-3/4 inches = 7-3/4 inches

Each of your contrast squares should be 7-3/4 x 7-3/4 inches in size.

Drawing a grid

Straighten the fabric into squares and cut out the squares with a rotational movement. Put the squares on top of each other, right sides together, aligning the edges.

Using a marking pen and ruler, draw two diagonal lines on the upper squares, from corner to corner. I usually mark the lightest square, but keep white markers handy to use when both squares are relatively dark.

Fasten the squares together with pins so that the fabric does not shift.
To sew

Sew a 1/4 inch thick seam on each side of each diagonal line. If you don’t have a quarter-inch thick presser foot, mark the lines before sewing.

Press the sewn square to align the seams – a step that eliminates small creases and facilitates the subsequent fit of the fabric.

Individual blocks

To divide a square into eight parts, you will have to make four cuts: vertical, horizontal and two diagonal. When making incisions, do not turn the fabric, otherwise your parts may shift in the right position! Instead, turn the mat or walk on it.

Vertical Use the central diamond-shaped shape created by the seams, the original marked lines, the lines on the mat and the sides of the shape itself to navigate when building a ruler. Using a rotating knife, cut both layers of the stitched square along its vertical middle.
Horizontally, use the same technique to cut your halved square into quarters.
Diagonals Finally, cut each of the remaining sections into pieces along the diagonal lines originally drawn.

You will know that you need to sew eight triangles from one fabric diagonally with eight triangles from the second fabric. Now it’s time to click.

Put eight unopened HST blocks on the ironing board. With the fabric, the seams will be pressed face up, press the unopened HSTS to secure the seams.
For each product, fold back the upper fabric of the backrest and use an iron (carefully) to open the product.

Now you have eight semi-square triangular squares!


Attached to the eight HST in the photo are small “dog legs” — tiny triangles that protrude beyond the seam when the patchwork quilt is pressed. Trim them before using.

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