Tips & Tricks: Making Half-Rectangle Triangles

If you've been quilting for a while, you are probably very familiar with Half Square Triangles (aka HST's). They're one of the most basic elements of most quilt blocks. I'm excited to have guest writer, Lisa from Wild Plum Lane, here to help us up our skill level - and design options - by helping make Half Rectangle Triangles! Can I confess something? In the past I've struggle with Half Rectangle Triangles and I'm so excited to try this handy trick from Lisa!

How to make Half Square Rectangles

Hi everyone! My name is Lisa Donnelly from Wild Plum Lane and I’m excited to be back with you today on the Diary of a Quilter blog to talk about Half Rectangle Triangles (HRTs). Whether you’ve made a million HRTs before or this will be your very first time, here you’ll find some tips, tricks, and tools to make half rectangle triangles easier to understand and easier to make.

Want to practice with me? Pull some fabric from your scrap bin and let’s work through the steps below to make a set of half rectangle triangles!

WHAT YOU NEED TO MAKE HALF RECTANGLE TRIANGLES (HRTs)

Today we will make a common size of half rectangle triangles, 2” x 4” finished (2.5” x 4.5” unfinished), and will make two HRTs in each direction. This method will leave plenty of room for trimming. Once you’ve made a few, if you’d like to change the size of the starting rectangles, you are welcome to do what works best for you.

WHAT YOU’LL NEED:

• (2) 3.5” x 5.5” light colored fabric rectangles (a great time to use scraps!)
• (2) 3.5” x 5.5” dark colored fabric rectangles
• A quilting ruler at least 2.5” x 4.5” in size with marks every ¼” OR specialized Half Rectangle Triangle trimming rulers 
• Fabric marking pen/pencil
• Wet erase or dry erase marker, optional
• Rotary cutter
• Cutting mat

ABBREVIATIONS

• RST = Right Sides Together
• HRT = Half Rectangle Triangle

HALF RECTANGLE TRIANGLES, STEP 1

On the back side of (1) light colored rectangle, draw a diagonal line from the top left to bottom right. On the back of the other light colored rectangle, draw a diagonal line from the top right to bottom left. They will look like the image shown below.

HALF RECTANGLE TRIANGLES, STEP 2

Here’s the first tricky part! With RST, align the top left of the light colored rectangle with the top right of the dark colored rectangle. The bottom right of that light colored rectangle should align with the bottom left of the dark colored rectangle. See below, left, for reference. Do the opposite with the second set of light and dark colored rectangles, as shown below.

HALF RECTANGLE TRIANGLES, STEP 3

As shown above, sew a ¼” seam on either side of the lines, then cut along the drawn line to create a total of (4) pieces, (2) HRTs from each set of light and dark colored rectangles. Press seams open or to the side, whichever you prefer (or according to pattern directions).

TRIMMING HALF RECTANGLE TRIANGLES WITH A STANDARD QUILTER’S RULER

Today I will share how to use a standard quilter’s ruler to trim your HRTs. You can also use a specialized HRT trimming ruler, if desired. 

Let’s set up your regular quilter’s ruler for trimming. 

First, let’s mark the 2.5” and 4.5” lines on the ruler at the top right (or you can switch this to the the top left if you’re a lefty!). I like to use either painter’s tape or washi tape to make it easy to see, as shown below.

This next step is important: Find the mark that is ¼” in and ¼” down from the corners of our marked 2.5” x 4.5” rectangle. While optional, I like to mark these with a wet erase marker so they can easily be found by my eyes as I trim, or dry erase markers could work too…whatever you’ve got on hand. I’ll refer to these as “alignment marks” throughout the rest of this tutorial. Marks from wet erase markers will stay in place as you work/move the ruler. If you use dry erase, you might need to re-mark a few times as you work!

You’ll make your marks at the following (4) locations on your ruler:

• ¼” x ¼” (for top right to bottom left HRT)
• 2 ¼” x 4 ¼” (for top right to bottom left HRT)
• 2 ¼” x ¼” (for top left to bottom right HRT)
• ¼” x 4 ¼” (for top left to bottom right HRT)

To trim, first line up the corners of the 2.5” x 4.5” marks on your quilter’s ruler with the diagonal seam of the HRTs. You’ll notice that the marked ¼” alignment marks are not aligned with the seam. This is a problem because if you trim with the seam exactly on the corners, when you begin to sew these HRTs together using a ¼” seam, the points won’t fall precisely on the corners.

But it’s a simple fix! A slight shift of your quilter’s ruler (clockwise, for top right to bottom left HRT on the left, below) so that the ¼” alignment marks fall exactly on the HRT diagonal seam will do the trick.

Trim your HRT to 4 ½” x 2 ½”, double-checking that the ¼” alignment marks consistently fall directly on the HRT seam. Trim your second HRT with the diagonal in the same direction in the same way. 

Use the opposite marked corners of your quilter’s ruler to trim the second set of two HRTs (with the diagonal in the opposite direction from the first set, shown above, right). Once trimmed, you’ll have (4) total half rectangle triangles, (2) in each direction. 

GET THE HALF RECTANGLE TRIANGLE CHEAT SHEET

Need a quick reference sheet with these diagrams and instructions that you can print out and keep by your side as you make your own half rectangle triangles? Head on over to my website to download your free printable cheat sheet today!

GET YOURS HERE

USING HALF RECTANGLE TRIANGLES IN QUILT PATTERNS

There are so many ways to use half rectangle triangles in quilt patterns! Simply adjust your starting fabric rectangle sizes and the ¼” alignment marks and tape as needed for the size of HRT specified in your pattern. While there are many fun quilt patterns that use the half rectangle triangle, one of my favorites is the Crystal Rose quilt pattern. 

The pattern includes plenty of opportunity to make half rectangle triangles since each of the diamonds you see in the blocks is composed of four half rectangle triangles. 

If this tutorial was helpful for you, I’d love to hear from you! Download your free half rectangle triangle cheat sheet, then head on over to Instagram to send me a DM or drop me a quick note to let me know how half rectangle triangles go for you. 

Thank you so much to Amy for having me again on the blog…it’s always fun to be here and to connect with each of you! Happy quilting!