The Tri- Rec Ruler Set is made for the triangle in a square unit (Doreen Speckmann called the unit Peaky and Spike)
The skinny triangle has angles of (approximately) 26.56, 90.00 and 63.44 degrees. The isosceles triangle has angles of approximately 63.44, 53.12, and 63.44 degrees.
IT WILL NOT WORK FOR MAKING EQUILATERAL TRIANGLES (or anything hexagon that uses the same size triangles)
Nor will a 60 degree angle ruler/cut work for the Peaky and Spike (triangle in a square) unit.