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.
Nine Patch Road
Free Quilt Block Pattern
The Nine Patch Road quilt block is a wonderful introduction to the nine patch block, as it contains a nine patch inside another nine patch.
This quilt block is a great beginner block, containing three different units -- the square, half square triangle and the flying geese patches. Playing around with colour can give you a totally different look.
By changing up the background fabrics, you can achieve very different quilts, as illustrated in the sample quilts shown. Sashing between the quilt blocks offers another chance to separate the blocks or add an additional fabric.