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.
English Wedding Ring
Free Quilt Block Pattern
The English Wedding Ring quilt block is based on a 5 by 5 grid, so the math is easy. This block can be sewn as a five patch or in the manner I have chosen to construct it -- as an uneven nine patch. Neither method is correct -- just a preference.
This quilt block contains only two different quilt patches -- the square and the half square triangle. These two patches are the most commonly used units in quilting.
The sample quilts illustrated show two entirely different looks, just by setting the blocks either as a straight setting or on point. Different fabric choices for all the finishing touches also contribute to the very different end results.
Related - Wedding Ring - (the different placement of colours yields a different quilt)