Conquer the Half Rectangle Triangle (HRT) Block – My Go-To Method for Sharp Points and Easy Trimming

If you’ve ever tried making Half Rectangle Triangles (HRTs)—you probably know how tricky they can be. Unlike Half Square Triangles, HRTs don’t have equal angles, and that makes trimming them a challenge. Even when you think the block is right, the points often go missing when you join them. Sound familiar?

I used to avoid patterns that required HRTs because no matter how careful I was, the blocks were hard to trim and even harder to line up. But after much trial and error, I finally found a method that gives me accurate size and clean, perfect points every time, without needing a specialty ruler or template.

In this tutorial, I’ll show you exactly how I do it, so you can enjoy the beauty of HSRs without the usual frustration!

I’ve found that the key to getting a perfect point in HRT is all about the ⅛" tip. Instead of aiming for a sharp point that touches the corner of the rectangle, you actually want the point to stop about ⅛" in. That small difference makes a big impact when joining your blocks!

⅛" tip.

Here’s why: when you sew with a ¼" seam allowance, the tip of the triangle will land almost right at the seam line! That’s why leaving a small ⅛" gap from the corner gives your block the room it needs for a perfect point after sewing it to other blocks.

I’ve explored several approaches for making precise HSR blocks—paper piecing gives flawless accuracy, and using a template also works well. But honestly, both felt too intricate and time-consuming for my workflow. So I found a much simpler method that’s just as accurate—and doesn’t require any specialty ruler (I don’t own one, so I can’t confirm if it would be compatible with this technique).

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Here’s how I do it

1. Two-at-a-time construction (just like for Half Square Triangles).

2. Instead of marking a true diagonal, I dot ½″ in from both corners on the wrong side of one rectangle.

3. I then connect those dots with a line—and you’ll see it doesn’t run exactly corner-to-corner.

4. On the second rectangle, I mark another dot on the right side, aligning it opposite the first set.

5. Sew ¼" seams on both sides of the drawn line, just as you would in the classic two-at-a-time Half‑Square Triangle (HST) method.

6. Cut along the drawn line to split the pair.

   

   
   
   

7. Press the unit open and trim it to the unfinished size—make sure the triangle tips sit about ⅛" from each corner. You may need to tilt or adjust the ruler slightly. Trim the right and top (or long) edges first

8. Rotate the unit 180°, realign using the line on the ruler, then trim the remaining two edges

   

   In this diagram, the green rectangle marks the line you’ll aim to cut along.

   

   

If you want the triangle to slant in the opposite direction, simply reverse the direction of the drawn line and how you place the fabrics.

HRT tutorial

Here is the complete Half Rectangle Triangle (HRT) size chart for 1:2 ratio blocks

Finished Block (in)	Trim to (Unfinished)	Cut 2 Rectangles (each)
1 x 2	1.5 x 2.5	2 x 3.5
2 x 4	2.5 x 4.5	3 x 5.5
3 x 6	3.5 x 6.5	4 x 7.5
4 x 8	4.5 x 8.5	5 x 9.5
5x10	5.5 x 10.5	6 x 11.5

I hope this makes Half Rectangle Triangles (HRTs) feel a little easier and less intimidating to make!