Because I had the triangle templates, I could measure the cut size of the sides of the triangles. Each of the non-bias sides measures 2 3/8 inches. On a blank sheet of paper, I drew parallel lines that were 2 3/8 inches apart.
Next, I drew perpendicular lines that were also 2 3/8 inches apart, creating a grid of squares each measuring 2 3/8 inches.
Then I drew lines from corner to corner in the triangles, connecting all of the triangles in the grid. These are the cutting lines that will create your half-square triangles.
Once the solid cutting lines were drawn, I drew dashed lines on each side of the cutting lines. These dashed lines are 1/4 inch away from the cutting lines, and they are sewing lines, giving each half-square triangle a 1/4 inch seam allowance.
In order to save fabric, I trimmed the excess paper off of the right side and top of the sheet of paper. This left a rectangle that measured approximately 8 inches by 11 inches.
Now this is ready to place on the fabric.
I placed the two pieces of fabric for the half-square triangles right sides together and then folded them in half, lining up the selvedges. In the picture above the top fabric is the white with green flowers, and is right side down, facing the green fabric..
Each of the triangle grids will create 24 half-square triangles. Each block needs 20 half-square triangles, for a total of 120 for this quilt. Therefore, I needed 5 of these grids in order to have the number of half-square triangles required for the quilt.
Remember, folding the fabric this way will result in 2 of the grid units being cut at a time.
To make it somewhat easier, I cut enough fabric off to create the number of grids I needed.
Lay the grid on the fabric, and cut a strip wide enough to extend slightly beyond the paper.
Each strip will create 4 grids.
Next I placed the grid on the strip so I could see how to cut each strip in order to have enough fabric to extend slightly beyond the length of the paper grid.
Then I cut the fabric around the grid, and it was ready to sew.
Separate the sewing units — the two layers of fabric that are facing right sides together. Pin a paper grid to each of the sewing units, and you are ready to take them to your sewing machine to sew.
Stitch on the dashed lines. You should be able to follow them completely around the rectangle of paper without removing it from your machine.
Remember to stitch all of the dashed lines. This means on both sides of the solid lines. You will cut the solid lines.
Once you have finished sewing on the dashed lines, remove the rectangle from your sewing machine and cut on the solid lines.
You will have 24 half-square triangles that need to have the paper removed and be opened up.
Remove the paper, and open them up to see triangles that are half green and half white.
By Penny Halgren of http://www.How-To-Quilt.com