A few weapons are fairly random in their accuracy and require you to roll a Games Workshop Scatter dice to determine where they land. This Scatter dice is marked on four sides with an arrow, and on two sides with a special 'HIT' symbol. Simply roll the Scatter dice near the target point, if an arrow is rolled this shows which direction the shot has deviated in. If a Hit symbol is rolled this generally means the shot is bang on target. Some weapons may scatter automatically, with no chance of a direct Hit, in which case you will find a small arrow on the Hit side to determine the direction.
Although a Scatter dice is the best way to determine random direction, you can achieve a similar result by using a D6. Put this book flat on the table with the arrow marked 1 on the diagram facing in the direction you want the weapon to fire. Roll a D6 and on a score of 5 or 6 the hit lands on target. If you roll 1, 2, 3 or 4 then the shot scatters, as shown. This method isn't as random as a Scatter dice but suffices in most circumstances.
Diagram: a circular scatter template with four numbered arrow directions radiating out from a central circle marked "5-6 (HIT)" — arrow 1 points up, 2 points right, 3 points down, 4 points left.