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
Auntie's Puzzle is an easy five patch quilt block (meaning that it is designed on a 5 x 5 grid), but I prefer to construct this block as an uneven nine patch. I just seem to have an aversion to sewing blocks in rows, rather than chunks, but do not let my opinion sway you. It is perfectly fine to sew it in rows if you are more comfortable with that. The instructions include measurements for 4 different sizes of the quilt block.
The two sample quilts illustrated look very different from each other. The quilt set with blocks side by side, use 90 degree rotations of the block to create a secondary pattern. The quilt blocks set on point have additional blank blocks and setting triangles to showcase your quilting skills. Enjoy your creating experience!