Which additional step is required for mortars during registration but not for artillery?

The correct answer is that mortars require an additional step called "Adjust the Sheaf" during the registration process. This step is uniquely necessary for mortars because of their specific firing characteristics and the way in which they deliver rounds to the target.

Mortars typically have a high angle of fire, which means that they can be more affected by the accuracy of the dispersion pattern, known as the sheaf. Adjusting the sheaf involves ensuring that the mortar rounds are impacting in a tight and effective spread around the target area. This is crucial for maximizing effectiveness, as mortars are often used in indirect fire roles requiring precise placement to suppress or destroy enemy positions.

In contrast, artillery systems, which generally use a flatter trajectory for their projectiles, do not require a sheaf adjustment in the same way. Their firing solutions are built around different methods and parameters that do not necessitate an adjustment to the dispersion pattern during registration.

Therefore, the requirement to adjust the sheaf is an essential and distinct step in the registration process for mortars that underscores their operational nuances compared to artillery.