Setting triangles are used when blocks are set on point. They are “fillers” that are used to make the quilt rectangular. Without these, you would have a zigzag edge. Four 1/2 square triangles are used in the corners. Quarter square triangles are used on the sides.
Setting Triangles: Notice the triangles below. There are 4 smaller triangles in the corner. These triangles’ legs are cut on the straight of grain (1/2 square triangles). The other 8 triangles are larger. The straight of grain lies on the hypotenuse (1/4 square triangles).
In the photo below, the ½ square triangle is on the top right. The other triangles are ¼ square triangles.
Learn more about setting triangles in the following 2 videos.
NOTE: to enlarge the video, click the PLAY button, then click the full-screen icon at the bottom right of the video.
TRANSCRIPT: Setting Triangles
In this quilt top we have examples of setting triangles; the triangles around the outside edge of the quilt. The triangles in the corner are called corner square triangles or half square triangles. The straight of grain is on this part of the triangle, it meets at a 90 degree angle. There are four of these; one in each corner. These triangles, the ones that are kind of in the middle here, all the way around the outside edge are called quarter square triangles. The straight of grain is on the hypotenuse.
So in order to set the squares on point, like these trees, you will need to use setting square triangles. If you look over in the corner at this small square that’s been set on point, you notice that they’re are just four triangles around the outside edge. If you only have one block to go on point then you’re only going to need those corner square triangles.