For an attack to be successful there must be a direct and
unobstructed line of sight between the designator and the target.
The distance between each pair of points was limited by the practical length of a measuring rod and the need to maintain an
unobstructed line of sight.
From the window ofhisllth-fioor New York Avenue office, one block east of the White House, attorney Robert Bennett--defender of presidents, cabinet secretaries and members of Congress--enjoys an
unobstructed line of sight to the Washington Monument and the best view of the U.S.
After all, if you've got time to sit down or kneel to use the short ones, you probably also have time to search about for a rock, tree limb or other rest--provided the terrain allows you an
unobstructed line of sight to your target.