Thanks! @Tapestry sorry for the quilting lingo! HST = Half-square triangle. It’s a square made from two triangles. My entire block is built from HST’s. Sewing a triangle is actually not fun, as when you cut fabric on the diagonal (bias) it tends to stretch. So, instead I put together two squares, and drew a diagonal line on the back. I stitched on either side of that diagonal line, then cut through the diagonal line, so instead of leftover triangle bits, I had an extra HST square. You can make them equal sized or make a bigger and a smaller HST, which is what I did.
ETA: and what @MistressJennie did in Ada’s Bonus Wall Quilt . It’s a clever way to deal with scraps, HST’s are very versatile.