Rafts are great fun and can be built from a variety of materials, basically anything that will float. Oil drums are popular as they are cheap, readily available, and incredibly buoyant when empty. You can design your raft to any specifications that you choose, but when building a raft, it is best to build it near a water source so you can test it without hauling it far.
Inspect each drum to make sure it is free of any holes. To prevent the drums from rusting in the water, apply a coat of rust-resistant enamel to the outside of each drum and allow to dry for 24 hours.
Lash your oil drums together side by side. Wrap a rope around the drums and secure with a square knot to hold the drums together tightly. For simple, single-person rafts, you can often go with just two or three drums; however, you can make the raft as large as you want.
Place wooden poles above and below the oil drums, in the joint where the drums meet.
Lash the top and bottom poles together using rope. This will clamp the barrels between them and keep the barrels in place.
Slide the raft into some still, shallow water and test the rigging once it gets wet. Tighten the ropes or re-lash if necessary.
To keep the oil drums from rusting from the inside, add a half-quart of used motor oil to the inside of the drums before sealing. Use pressure-treated lumber to prevent the wood from rotting in the water.
Follow all boating safety precautions, and always wear a life vest.