The heater hose is connected to the bib at the back of the engine RH side near distributor. From there it goes to the heater core. A return line goes to the front of the engine (LH side) and connects to front timing cover and ultimately to the water pump. You need to circulate the water from one end of the engine to the other. People don't like the heat that is generated in the heater box even though the heat temp setting is set low so they attempt to block the hose and thus screw up the engine cooling. I better device is a valve that controls the flow of the water to the heater box. When closed the valve bypasses the heater box but allows it to continue to the block. When valve is open water goes to the heater core.