A bisector line in this context is a STRA element that bisects the angle included between two existing linear elements. Its FPT is the intersection point of the two existing linear elements and its TPT lies on a line joining the FPT to the SHEE boundary. (The two elements need not actually intersect; the intersection point is derived by projecting the elements if necessary.) Starting with a STRA as the current element, a bisector line is created using the BISECT command to define the two lines to be intersected. For example: