Flying Geese 2" x 4" ruler locks onto seams for instant ruler placement, control so that the seams end in each corner and trims the correct amount across the tip. Ruler rock is gone, too. Once the unit is completed and trimmed, it will measure 2 1/2" x 4 1/2". Trims full and partial flying geese, parallelograms, square in a square and many. many other types of flying geese.