See the attached document which describes Positions of Responsibility held by Scouts in the troop.
How is Youth Leadership Organized?
Leaders of the Scout-Led Troop
A Scout troop is a small democracy. Withe the Scoutmaster's direction, the Scouts are formed into patrols, plan the troop's program and make it a reality. In order for that to happen, a troop relies upon Scouts serving in positions of responsibility. The key leaders of the troop make up the patrol leaders' council. They are the senior patrol leader (SPL), assistant senior patrol leader(s) (ASPL), patrol leaders and troop guides of any new-Scout patrols.
How are Leaders Selected?
Senior Patrol Leader
The youth leader with the most responsibility in a troop is the senior patrol leader. The SPL is elected by members of the troop.
Assistant Patrol Leader
With the approval of the Scoutmaster, the ASPL is appointed by the SPL.
One patrol leader is elected by the members of each patrol.
Other Troop Positions (quartermaster, scribe, historian, librarian, chaplain's aide, etc.)
The SPL selects the Scouts who will hold each of these positions.
Depending on the size and needs of a patrol, any or all of the following positions may be filled; assistant patrol leader, patrol scribe, patrol quatermaster, patrol grubmaster, patrol cheermaster, etc.
With guidance from the Scoutmaster, it is up to the patrol leader to select a Scout for each position.