The top left and bottom right sections or '4 patch' of this block are made up of 'triple triangles'.
This technique can be used in making the Farmer's Wife Sampler blocks:
#27, #28, #51 and #91.
Here's a tutorial on how...
First...create half square triangles
Press open to create 2 half square triangles
(which i forgot to take a picture)
Sew to a rectangle which measures the same width as the half square triangle plus 1" longer than the half square triangle.
Stitch these two units together like so...
Make one clip almost to the seam
and press seams in opposite directions.
click to enlarge photo for a closer look
Next, line up a 45* line along the outside of the block and draw a stitching line. Do this again to the opposite side.
Should look like this.
Add a second rectangle measuring the same size as the pieced unit. With right sides together stitch directly on the drawn lines.
Cut a quarter inch beyond stitched line...between the lines
Press open for a 'triple triangle'.