More to explore:
Sewing Half-Square Triangles
half square triangles made easy
Half-rectangle tutorial- I love everything about this
Half-square-triangle short-cuts and easy square-up - Diary of a Quilter
SuperGirl ( HST )
Half square triangle chevron
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.
using hst to construct pattern
No-mark Stitch & Flip. Easy way to make half square triangles, etc.
How-to make 8 HSTs (Half-Square Triangles) at one time. KatiesQuiltsandCr...
a²(w): HRTs (half rectangle triangles) tutorial