While it's always best to pack your sleeping bag in the bottom of your backpack to keep it protected from moisture and wear, a full pack can sometimes necessitate storage outside of the backpack. External frame packs are generally designed to accommodate a sleeping bag underneath the main pack, so attaching one is not a difficult task.
Pack up the rest of your gear in the backpack. The sleeping bag will be the last item that you secure to the backpack.
Pack your sleeping bag into a waterproof dry sack or plastic bag. Close the sack and ensure that it's fully sealed. You never know when the weather might change, and you shouldn't risk getting a waterlogged sleeping bag.
Get a pair of accessory straps. In order to attach the sleeping bag to the backpack, you'll want a pair of straps. You could also use rope or twine in a pinch.
Place the sleeping bag on the frame underneath the main backpack compartment. Center it between the left and right side and place it as close to the pack as you can.
Wrap the straps around the metal frame or connection points on your backpack. Wrap one around each side of the sleeping bag, about two inches from the ends of the bag.
Thread the strap through the plastic buckle. Just like the straps on your backpack, accessory straps are designed to be pulled tight and then secured in place with a plastic buckle. Push the first strap up through the buckle, pull it tight, and then push it back down through the lower slot. Repeat for the second buckle.
Adjust so that the sleeping bag is secure and stable. You want the straps digging into the sleeping bag to the point that it won't bounce around or fall out when walking.
Tie up or tuck away any loose, dangling strap ends so they don't catch on anything while hiking.
- Jana Foster/Demand Media