This way, you can walk around, with two, one or no hands on it. Strong hand on the pistol grip, the free left hand can open doors, move branches etc.
For climbing walls or trees or more comfortable "garrison carry" just slip your strong arm under the strap, and let it ride on your back, muzzle down. Reverse this to bring it to ready position, that is, strap behind neck, both arms outside of the strap, on or near the weapon.
This is not quite as good as wearing a modern tactical harness and 3 point sling, but the advantage is the entire one-piece sling always stays on the rifle, 100% ready to throw over your neck, battle ready. You don't have to 'suit up' and snap on the rifle to be ready. It's how I do it. It works.