I've seen this technique, but I'd never tried it. It begins with HSTs (Half Square Triangles). Make these as usual by pairing two squares, drawing a diagonal line, stitching on both sides of the line with a .25" seam, and cutting on the drawn line.
Next, you pair your HSTs as shown below. With right sides together, place one HST atop another. The seams will line up and nest, because you are putting contrasting colors together. In this picture, my bottom HST has the red on the upper half, and the top HST has the red on the lower half.
Draw another diagonal line and stitch on both sides of it, just as you did before.
Make sure your seams line up. I placed a pin in the middle, to keep the seams nested.
After stitching, cut on the drawn line and press the block open.
Congratulations! You now have two hourglass blocks.
Mine measured approximately 6.25", so I trimmed them to 6" to make sure they were square. I lined up my diagonal line on the ruler with the diagonal of the square. Note that I place the ruler so the 3" mark was exactly at the center where the triangles meet.
You can arrange the blocks in different ways:
I wanted to see them in combination with some four-patch blocks, so I made a few with 3.25" strips.
Here are a couple of different layouts:
|Sorry about the blurriness of this picture!|
In the top layout, the four-patches are each surrounded by four matching triangles. In the second, the four-patches are surrounded by two different colors of triangles.
I'm not yet sure how I will put these together, but I did find out the size of the hourglass block made from 7" squares which was what I set out to do in the beginning. Sometimes, you just have to experiment to find your answers. :)