If you don't have a backpack with a detachable daysack, you will need to combine your rucksack with a smaller carrying option. A shoulder bag works very well in conjunction with a a backpack or day bag on your back. Waist bags are a very comfortable way to carry your bits and pieces, offering easy access and a certain amount of added security. Some have water bottle compartments - ideal for walking/cycling. They work well with a day pack to keep your camera, maps, sunscreen or any other bits and pieces you may need in a hurry. It gives easy access and can be used on its own when you can lighten the load.