realexplodingcat | Parental Observation Of The Day

It's a good thing babies have armpits. Otherwise, they'd slip right out of your hands every time you try to pick them up.

The same can ALMOST be applied with adults.

But the full nelson is a bit more effective.

Armpits are essential for the full nelson. Can it be applied to someone without a head though?

Yes. However, in extreme cases (as if not having a head is extreme enough), it ends up becoming the Heimlich Maneuver.