How To Sew Half Square Triangles (HST) with Directional Fabric


Exciting news!  My hubby and I are expecting!  We found out we’re having a girl who is due in early September.  We’re very happy.  Obviously I love to sew, so I wanted to make a baby quilt to celebrate and to use as the first item in our nursery.  Being fairly new to quilting, I heard a baby chevron quilt using half-square triangles (also called HST) was a realistic quilt to make.  As beginner as it was, I ran into a few problems because of the directional fabric I chose!  This post is about how to make half-square triangles and also about how to make them with directional fabric.

See the aqua fabric with the bird cages?  See the pink fabric with the leaves?  Those are considered directional fabrics because the print is going in one or 2 directions.  The other fabrics are non-directional because you can lay them down in any way and the direction doesn’t matter.  (Fabrics I used are all Keepsake Calico Prints from Joanne.)  For quilting, directional fabric can be tricky to use… hence what this post is all about!

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To start, let’s all be on the same page with how to make a half-square triangle (HST).  You need 2 pieces.  I used a white 5″ square with each of my 5″ patterned pieces.  (5″ squares can also be called “Charm Squares.)

Step 1: Draw a line down the centre, corner to corner, of one of the patterned pieces.  I used pen because it will be cut through later.  If you’re using directional fabric, this step needs to be carefully planned (explained later.)  If your fabric is non-directional, it doesn’t matter which corners you draw your line through.

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Step 2: Lay the patterned piece over the white piece, right sides together.

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Step 3:  Stitch on either side of the marked line 1/4 of an inch.  I used my 1/4″ presser foot as a guide.

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If you prepare a lot of squares at once you can “chain piece” them together like this!  First, I sewed 1/4″ on one side of the line on all of the squares, then I turned it around and sewed on the other side of the line on all of the squares.

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Step 4: Cut each square in half along the centre line you drew in pen.

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Before you know it, you have a ton of HST’s waiting to be pressed!

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Step 5: Press each triangle open so that the seam lays below the darker fabric (in this case the patterned fabric.)

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Step 6: After sewing, each square is no longer a perfect 5″.  They are roughly 4.5″ squares so it’s a good idea to trim them a bit!  Use a square ruler as a guide if you can.

With the 45 degree line on the ruler laying over the seam on the square, measure a 4.5″ square and trim the edges.  Rotate the fabric square to the other side and trim those edges too.

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See that little seam allowance sticking out on the right?  give it a trim!

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So…at this point, I thought I was ready to sew my quilt in a chevron pattern but when I laid out the squares, the direction of the fabric was going all different ways!  ROOKIE MISTAKE!

Here is an example of what happened.  See how the birdcages on the left HST are upside down and the birdcages on the right HST are sideways?  I want them all to be right side up!


To give you an idea of what it’s supposed to look like, here’s a picture of it after it was fixed.  See how all the bird cages are all right side up now?  The way to use directional fabric with half-square triangles all lies in where you place your seam.  As you can see, for each HST, the seam is going on an angle towards the right or to the left.

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To really see what I was doing, I took each square and folded it so that each seam was going up to the right or to the left while making sure that the pattern on the fabric was right side up.  I laid them in a pile.

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Then, one at a time,  I marked the back of each piece with a pen at the same place where I folded square.

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I sewed them together with white squares and all the HST’s were perfect!

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YAY!  The beginnings of a cute baby quilt for our new arrival on the way, xo.  I’ll tell you how I finished the quilt in my next post.

You can find another useful blog post on this topic here.

If you’ve done this before and have any more tips, please feel free to comment!  Thanks!

Happy sewing,



6 thoughts on “How To Sew Half Square Triangles (HST) with Directional Fabric

  1. Thanks for posting about this. I hadn’t thought about this, though I am a relative novice as well. I feel like I really do “learn something new every day”. But learning from experience can be a little painful! Congratulations on the new baby! Children are a wonder.

  2. Great advice! I had difficulty with directional fabrics when I first start quilted, and if I had’ve seen your post way back when, I would’ve been able to fix them up easily! Look forward to seeing the end result. And congratulations! 🙂

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