This dual purpose ruler allows you to mark the center of your block/strip/fabrics within a 12" span as well as easily mark your sewing lines for half square triangles. There are markings
Simple Half Square Triangle Quilt - Freemotion by the River
Quilt Ruler Options for Trimming Half Square Triangles (HST)
Half Rectangle Triangle Ruler - by Southern Charm Quilts (C39204)
Create 8 half-square triangles with only 4 seams and 4 cuts. Template creates 11 sizes of half-square triangles from 1-5/8''--6-1/4'' Laser-cut
YICBOR Easy Half-Square Triangles Quilting Rulers and Template
Simple Half Square Triangle Quilt - Freemotion by the River
How-To Square Up Half Square Triangles - Gigi's Thimble
Rahoe's Product Review blog. - Blog
Time-Saving Quilting Technique: Half Square Triangle Shortcuts
Simple Half Square Triangle Quilt - Freemotion by the River