What step is required for mortars during registration but not for artillery?

The correct answer highlights the need to adjust the sheaf specifically for mortars during the registration process. This step is crucial for mortars because they typically have a more substantial spread of fire due to their indirect fire nature and various factors like projectile drag, angle of fire, and environmental conditions. Adjusting the sheaf ensures that the mortar rounds land in the desired area for effective targeting, enhancing the accuracy and efficiency of mortar fire.

While artillery also requires adjustments for accuracy, the specific step of adjusting the sheaf is uniquely emphasized for mortars during their registration process. Artillery systems may focus more on achieving accurate target locations through other means such as adjusting for range and deflection, which do not necessitate the same emphasis on sheaf adjustments seen in mortar operations.