I've been thinking of doing a series of building blocks type tutorials for a while now.
I'll be doing mini-tutorials on different types of blocks that are typically pieces in larger more complex blocks.
This is the half square triangle.
Cut one square of your light "finished square" + 1 inch by "finished square" + 1 inch.
Cut one square of your dark with the same dimensions.
If you do not like trimming your squares make the dimensions for your squares "finished square" + 7/8".
On your light fabric, draw a line along the diagonal.
Line your squares up for sewing, right sides together.
This is what it will look like when you've finished your sewing. Cut along your drawn line to create two blocks.