The 4-patch unit is thought to be one of the simplest constructions in quilting. It is based on a 2x2 grid as shown in the example block above. Most units are formed by attaching two squares together, then attaching another set of two squares.
A more efficient way to make four-patch blocks is with strip piecing. Sew strip sets with two long strips of fabric together, then sub cut those strips into the correct size to form your two-square units.
If you are careful to press your seams in opposite directions, you get a nice little nesting effect where the seams meet up. As you assemble the pieces together to sew them you can actually feel where the seams nest.
Alternate Grid 4-Patch
It is also possible to construct a 4 patch unit based on a diagonal grid, like below:
In this case, you sew together the two triangular units on each side of a diagonal line through the grid, then sew the two sides together. The seams in the middle still nest like they do in a regular 4-patch.
More elaborate 4-Patches
Any block where you are able to visually cut it in half horizontally and vertically into a 2x2 grid is still basically a 4-patch. Sometimes, you might have to examine the block before you see it. Below are a few examples:
To make any 4-patch construction lay flatter, try collapsing the center seam. Instructions are found at the bottom of the 4-Patch Unit page.