To make a pig roaster, cut an oil drum lengthwise to form two sections, attach a handle to top section, drill ventilation holes, fix a grate, build a frame to hold the roaster, fit a rotisserie spit, and insert the roaster in the frame. Light a charcoal fire, and test your work.
Purchase an oil drum of desired length. Clean the drum with a rag and soapy water. Cut the drum longitudinally with an angle grinder to get two sections namely, the top lid and bottom cooking area. Place two brackets with hinges on the lid, and use bolts and nuts to fasten it to the bottom section. Use bolts to secure a handle on the lid.
Drill about 20 half-inch holes in the cooking section for ventilation. Measure the length and width of cooking section's opening, and use the measurements to purchase a grate. Position the grate on the top of the bottom section. If necessary, attach metal covers and a retaining screw to hold ash in place. After adding a grate and ventilation, cut eight pieces of steel as appropriate. Weld four pieces to create the top section of the frame, and then fix four legs.
On the outside of the grill, install two steel casters at the top and bottom of the drum, and fix a 1-foot steel rod on the top of the roaster to create the rotisserie spit. Attach a handle on the rod's terminal. Fix the roaster in the frame, add charcoal, light a fire, and roast your pig.