Many Drillers who are not aware of what the stacking swivel is and what it is used for assume it is another swivel for attaching a sling, especially since most slings purchased today are very unnecessarily long (if you cut about 6 inches off of the sewn end, it will fit just fine). Here is a typical example:
Even some staff members at Daisy are unaware of purpose of the stacking swivel (image courtesy Daisy.com).
FYI: the nomenclature of a rifle:
The M1 Garand Nomenclature
The Stacking Swivel
This part of the rifle was used constantly used when the rifles were first made (M1903 was made in 1903…). You don’t see it on modern rifles because their either too short (more mobility for the military), or if they are long (variants of the M1903 and M14 are still going strong today mainly as sniper rifles), their use is small in scope and not many rifles like them are issued in a units (unlike long ago, when everyone in the unit had the same rifle) making the stacking swivel useless (no other rifles to hang around with).
Years ago (as far back as Colonial times and as recently as WWII, and currently, in some cases), Soldiers needed to be able to leave their rifles in a certain area without laying them down in the mud and water. The Army developed the command and procedure, Stack, ARMS. Like Sling Arms, the procedure is not meant to be executed sharply, in unison. Every three Soldiers would be a group to Stack Arms.
As you can see from the picture at left, the rifles form a tripod and thus stay out of the mud and grime. Stack Arms is an alternative to Ground Arms (not as sharp, though) for firing parties of certain funerals where the pall bearers also pull duty as firing party if necessary. The picture below shows how three rifles (Daisy Drill Rifle M1903 replica rifle) are put together for Stack Arms.
Civil War Era rifles at Stack Arms
Courtesy of Katelynthomasphotography.com
Soldiers in Formation (WWII era?) with Rifle at Stack Arms
m1903, m14, m1 garand, rifle, stacking swivel, stack arms, upper band, sling swivel