Bloc-Loc 4.5" Inch Ruler - Half Square Triangle Ruler
Bloc Loc Ruler, 4 1/2"
This ruler is perfect for squaring up half square triangles to 4 1/2". Bloc Loc's half square triangle rulers make the tough job of squaring up easy and fast. The groove slides along the seam to keep the ruler from slipping when trimming smaller units, and allows quilters to rotate the block without lifting the ruler.
Unsure of how this great tool works simply view this video on using the Bloc-Loc rulers.