This Half Rect Ruler helps you trim precise half rectangle triangle units quickly and easily. The finished unit is twice as tall as it is wide, a ratio of 2:1. Create seven different size units from 1 ½ in x 2 ½ in to 4 ½ in x 8 ½ in - 1 in x 2 in to 4 in x 8 in finished size. Fabric is first cut into rectangles following the chart provided in the written instructions. The rectangles are then sub-cut into triangles using the markings on the Half Rect Ruler. Once sewn the units are easily trimmed to the exact size desired.