Originally Posted by PaperPrincess

Very often you can use one of your 'normal' rulers for everything. You can use the angle lines on the ruler to cut 30, 45 and 60 degree angles, which are very common. Unfortunately, if you need to get a triangle-in-a-square patch, that angle is around 65 degrees so you can't cut it with your 'normal' ruler. So for this particular quilt, you need to get a tri-recs ruler. As far as rulers go, this is not very expensive, you can get it at jo-anns with a coupon. Seems to me they also sell it in a set with the companion ruler, which cuts the long skinny triangles.
Many, many star blocks use this patch, so it would be a worthwhile investment: Tenessee waltz and alberta star quilts come to mind. Stars that are based on a 9 patch (3X3 grid) use a triangle-in-square, stars that are based on a 4X4 grid use flying geese. Not the same angle!!!!