FLIGHTCHECK® defines a hairline to be any line, frame or paragraph rule which is drawn using a linewidth less than .25 of one point (where a point is 1/72 of one inch). A hairline is defined in postscript terms as a "zero" linewidth, in other words the width of the smallest dot that can be drawn on the device. For a high-resolution output device the line will be printed so finely that it will often appear to be "broken".
