Cut the four pallets in half. Measure the side of the pallet that is 48 inches and make a mark at 24 inches, which is center. Use a saw to make the cut all the way across the pallet, leaving you with two pieces from each pallet. You will end up with eight cut pallet pieces, each 24 inches long by 20 inches wide.
Use the wire cutters to cut 16 pieces of wire 8 inches long.
Stand up the first and second pallet pieces at right angles so that corners are as close together as they can get; these will make the first two sides of the bin. Use one wire toward the top of the pallet to tie the two pallets together. Tie the second wire at the bottom of the pallet. Add another wall and wire tie together. Add the last wall and wire together. Now you have the first bin, which is 24 inches high with 20-inch wide walls.
Construct the second bin the same way as the first, using the remaining wire and pallet pieces. Place the two bins side by side. Use wire to tie the bins together if you want to..
Make the cover using two 40-inch 2-by-4s and two 20-inch 2-by-4s. Nail them together to form a 40-inch by 20-inch cover. Staple a piece of 20-inch by 40-inch plastic sheeting to the top of the cover.
Attach two door hinges to the back 2-by-4 and to the pallet wall, placing one on the left side and one on the right side. This will allow you to lift up the cover and close it after adding waste or turning the compost pile.
Add the waste to the compost bin. Every week or two, open the cover and use a pitch fork to move the waste from one bin to the other bin. The next time you move the waste, move it back to the first bin. This method of turning will help speed up composting.