An implement Frau Blücher would understand.
Sternum Strap: A narrow piece of webbing that lies across the chest, connecting the shoulder straps and enabling loosening or tightening for comfort and fit.
Sternum Strap: A strap that connects the two shoulder straps together. It helps to bring the weight of the pack towards the torso.
Sternum Strap: A strap that connects the two shoulder straps together. It brings the weight of the pack toward the center of the hiker's center of gravity.
Sternum Strap: An addition to a pack which allows it to hug the hiker as tightly as a tick hugs a leg hair. As tightly as an alien face hugger wraps around a head. You get the idea.