Set a 55-gallon plastic drum on its side. Place bricks or rocks on either side of it to prevent the barrel from rolling.
Draw the outline of the entry door on the top side of the barrel. The entry door is a hinged panel that you can open to gain access to the inside for placing your compost material. The door can be as big or small as you like, but 24-by-15 inches is a good reference size. Draw the outline of the door with a permanent marker.
Place a set of hinges on the top side of the door. If you are making a 24-by-15 inch door, place the hinges along the 24-inch-long side on the top of the barrel. Mark the bolt holes with your marker so you know where to drill. Place a set of latches on the other 24-inch-long side of the door, parallel to the hinged side. Mark the bolt holes for the latches with the marker. Remove the hinges and latches from the barrel.
Drill out pilot holes that you marked for the hinges and latches.
Cut out the outline of the entry door with a jigsaw.
Squirt a small amount of Loctite or other plastic adhesive in and around all of the pilot holes you drilled. Bolt the hinges and latches to the barrel with the installation bolts and nuts. The adhesive will help keep the bolts from moving inside the pilot holes.
Drill several 3/8-inch-diameter holes in the top and sides of the barrel. This will allow the compost to breathe, which will make it usable in less time.
Open the entry door and put your composting material inside the barrel. Shut the door. Place the two clasps through the latches to keep the door from opening.
Remove the bricks or rocks from the undersides of the barrel. Rock the barrel back and forth to thoroughly mix the compost. The compost should be ready to use in about three weeks.