Stacking Arms was an important part of drilling. It requires the close coordination of four soldiers, the front one and twos, and their corresponding rear one and twos.
The front two has the most important job in starting the formation of the stack. The excellent video below created by the 124th NYSV Reenactors pays hommage to the influence of Regulars on the need for state units to improve their drilling.
The 3rd US Regular Infantry Reenactors make sure all members learn how to properly stack and unstack arms.