The article lists the tools necessary for trajectory determination with the use of string. Guidelines are outlined for performing string trajectory determination when the bullet holes are in the windows of vehicles and in a building structure. The recommended general procedure is to first catalog a visual inspection of projectile impact sites with a diagram, measurements, and photography. A preliminary test should then be conducted with the laser beam. This may well provide the investigators with a baseline of information with which to conduct further testing. The second part of the examination is to attach the string from the impact site outward in the direction from which the projectile was fired. It is helpful to have a set of PVC upright poles to which to attach the string once the angle of impact has been determined. The attachment position is based on the angle backtracked from the impact location and angle. The shooter's relative position and distance from the target can often be determined from this test. Upon completion of the string attachment and pole placement, it should be double-checked with the laser pointer. Minor adjustments are often made during this review. This article also explains injury analysis on live or dead subjects, some problems in performing string trajectories, problems with laser light, and a demonstration of the string technique in open court. The author cautions that the trajectory determination with this method is not exact, but is valid as one of several methods of determining the point of convergence or origin of a projectile. 7 references