More to explore:
a²(w): HRTs (half rectangle triangles) tutorial
HST technique. Begin with 2 squares of fabric and end with 4 squares of half square triangles. Plus an extra step to make many unique blocks.
squares with triangles in opposing corners.
half square triangles made easy
How-to make 8 HSTs (Half-Square Triangles) at one time. KatiesQuiltsandCr...
Sewing Half-Square Triangles
Half square triangle chevron
Diary of a Quilter - a quilt blog: Half-square-triangle short-cuts and easy square-up
Quick and Easy Half Square Triangle (HST) Hack
how-to quilt square
Square spiral quilting tutorial
No-mark Stitch & Flip. Easy way to make half square triangles, etc.