Now this is cool! A McGuire rig, used to extract US Special Forces from hot LZ’s in Vietnam, heres the matter of fact explanation by one, “What we did was tie our rappelling rope around our chest, then snap a d-ring on the rope. As our chopper was hovering above the jungle at tree top level, the crew dropped two or three one-hundred foot ropes down to us. These ropes had a loop at each end and were securely tied to the floor of the Huey. We snapped the end of the rope to our d-ring and were lifted out of the jungle then flown to the nearest LZ (Landing Zone)…”.
What he doesn’t mention is the fact you’re being shot at while this is happening and that some people occasionally fell out. Which is why it got replaced by a better design thankfully!