The Lightweight tropical rucksack is attached to the frame on the lower bars. The lower position is the standard, but can also be attached to the frame in an ‘Upper Position’. If you havent done this before it can be quite tricky.
Attaching in the Lower Position
If you have the back of the rucksack facing you you will see two straps and buckles like those in the above picture.
Put the rucksack down with these straps facing towards you. Then place the rucksack frame on top. The curved section is towards you with the middle frame bar positioned as in the photograph.
Place the two straps between the three cargo buckles. Loop one of the straps through its own buckle and back on itself. Repeat with the other strap.
Next secure the sides of the rucksack to the frame using the frame securing straps. The result looks like below……
The Last Patrol 
You guys are fantastic! I have had one of the light weight packs since I was about 12-13. Used it extensively when I was younger. Have not used it for years and finally dug it out. Mud dabbers had made some nests in it so I took it apart to wash it. Spent hours trying to put it back together properly. Mine is in nearly perfect shape but was set up with the pack at the top of the frame. Assembled it, with the pack at the bottom. Going to try it this way. However, if someone has the directions to assemble it with pack on top, it would be greatly appreciated. Again thank you for your web site. David
Hello I am a fellow reenactor. I do war between the states. I have come in possession of a Vietnam era ruck sack. I am a Deputy and did some home repairs for my sergeant and he gave it to me.Through my research I believe it to be an 1976-1977 light weight ruck sack. I have the frame and all original straps accept the middle horizontal back strap. The US stamp is still highly visible and it still has the instructions in its top flap. It is in great condition I have carried camping several times with my sons scout pack. I am wondering how much it could be worth. But i am on the fence on selling it. I have thought about keeping and using being that my grand father and several of my uncles went to Vietnam. While i know It is not one of theirs it still holds value to me for that reason. If i were to keep it i would like to know If you had links and/or suggestions on load placement . Thank you for your help and look forward to hearing from you. Also do you know of a group that is here in Ga being that I live here and might be interested in attending and maybe participating.