The dry run is part of the rehearsal for a terrorist act,[1] and is often the immediate precursor to the attack.
[2] It may include attempting to smuggle weapons or other items to be used in the attack past a security checkpoint to determine whether this will be noticed, or monitoring the reactions of security personnel to the actions that would occur during a real attack.
The dry run is considered to be the heart of the planning stages of the terrorist attack.
[3] It is the method by which strengths and weaknesses in the plot are exposed to the terrorists, unforeseen obstacles can be detected, and the techniques are refined.
[4] Sometimes, multiple dry runs are conducted in an effort to perfect the ultimate attack.