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 Entwined Star quilt block is a standard nine patch featuring half square triangles and quarter square triangles. The centre patch is made with a square in a square unit. All of these are common patches.
Just to mix it up a little, I have given instructions for the "sew and flip" method of making the small corner triangles in the majority of the patches. These are created with small squares which are sewn down and then flipped back to form the triangle in the corner -- hence the technique name.
The two sample quilts illustrated are both designed using on point settings -- but give two totally different results.
As a side note ~ You might also be interested in a similar looking block called Frolic. It is created using only half square triangles. (I also noticed (after the fact), that I used similar fabrics for the Frolic block.)