I guess you screw a 1/4" male threaded nozzle in one end and 1/4 " male threaded barb in the other to connect to your hose and then push fit inside the number 2 section of the pole ( number 1 removed ) 
The reason why no 1 section is removed is because it will not fit otherwise or the pressure washer hose and couplings inside. Also if somehow you managed to rig something up using the no 1 section aswell it would be too wippy to use at high pressure.
Same goes if you wanted to use it as a softwash high volume, low pressure pole as you need the space inside the pole to fit a larger hose and couplings.
My only concern is what metal it's made from as if using say a strong bleach mix will it last very long.