Examine each of the pallets for sharp edges and nails that stick out of the wood. Use a hammer to drive any nails back down into the wood.
Place two of the wood pallets end to end on the floor.
Place a 12-inch 2-by-4 on the inside edge of the pallets where they meet. Six inches of the 2-by-4 need to be on each side of a pallet.
Secure each end of the 2-by-4 to the pallet with clamps. Drill pilot holes into the pallet and 2-by-4 with the power drill. Secure the pieces of wood with screws. Repeat this step with a 2-by-4 on the other side of the pallet.
Sand the top and sides of the pallets with sandpaper or a hand-held sander to smooth any sharp edges.
Place the third pallet on the floor where you want to locate the bed and set the joined pallets on top.
Set the mattress on top of the platform to complete the bed.