The Yokohama walking shop, Kamoshika, gives out a couple of bags to those who join their loyalty scheme. Then, rather than hand over a card at the cash desk you wave a bag and they take n% off the purchases as they put them in the bag. One of the bags is perhaps the most simple rucksack there is. Basically it's a drawstring nylon bag, but the strings are webbing and attached to rings in the bottom corners, so it can carried on the back.
When we went to volunteer in Ishinomaki, we couldn't carry that much stuff so James took this extremely lightweight rucksack and it worked out well, so I decided to make one for me. I also added an insert to both bags to allow a Platypus water carrier to be carried a little separately from the other things in the bag. The pattern for the main body is pretty simple - just a rectangle with some folds in. The metal rings came from the make your own handbag section of Swany, in Kamakura. The seams in the original and the copy are bound with tough binding so that the binding takes some strain off the fabric. I made the bag out of left over trench coat fabric, and the Platypus holders are made of Pertex.