The half square triangle unit is probably the most commonly used patch in a quilt block -- well it is second only to the square. It is made simply with two triangles, filling up half the square each -- hence the name. Take a quick look through this website, or in any quilting magazine, and you will start to notice that this half square triangle, regardless of its size, is present in more quilts than not.
Free Quilt Block Pattern
The Free Trade quilt block is an easy nine patch block comprised of three simple components -- the square, half square triangle and flying geese units. Imagine the possibilities when you play around with your colour choices.
For the sample quilts shown, I feel this block should be called "Luck of the Irish" or something similar. However, that is simply because the quilts are all in various shades of green. By simply changing up your colours you will have a totally different looking quilt. Just be sure to have the same contrast between the light, dark and medium fabrics.