propogate celtic knot centers

To find the next center construct a radius of 45 degrees 2 units long and then draw a right angle that leads to the horizontal construction line which should be drawn lightly to be erased later. Then draw concentric circles with diameters 3 and 5 units measure. You can measure the distance between the first two centers with the compass and then mark off centers on horizontal construction line. See Photostream and album

Done