Many businesses will give away wood pallets that they no longer use. In repurposing these for raised beds, do not reject a pallet because it has some broken planks. Do avoid using pallets that may have come into direct contact with toxic chemicals; these may leech into the soil of the raised bed. Pallet sizes vary, and you may have to trim the edges to remove defects, so the usable wood will dictate your final bed size.
Remove all nails. Use the claw side of the hammer and pry up the nails holding the top pallet planks to the support braces. Use a crowbar to pry apart pieces of wood. Hammer exposed nails on their pointy side and drive them out of the wood.
Select the location for the raised bed. Choose a spot that receives several hours of full sun for flowers and vegetables and a shady location for hostas and ferns. Measure the area, being prepared to revise the measurement to fit the wood dimensions.
Examine the wood planks. Select the planks in the best condition. Separate the planks into two groups of four planks each. Designate one group of planks as the sides and the other group as the front and back. Collect an additional set of four planks to serve as stakes to hold the raised bed in place. Choose stakes that are long enough to extend past the raised bed at least 1 foot into the ground.
Use a circular, hand, chop or jigsaw and cut the side planks so that they are equal in length. Cut each front and back so that they are equal in length. Do not make the planks longer than what will fit in the area you measured for the finished bed.
Take the planks for the front of the raised bed and lay them side by side, with the long edges adjacent to one another. Find the center point of the planks and place one of the stakes at the center point. Position the top of the stake flush with the top of the long edge of the planks. Nail the stake to both planks using galvanized or other nails rated for outdoor use. Nail stakes to the back and sides.
Position the planks so that the stakes face up in the air. Place the front section where it will create a corner with a 90-degree angle with a side section. Nail the front to the side section. Nail the other side section to the other end of the front section. Nail the back to the sides.
Dig holes for the stakes. Turn the frame over and push down into the ground. Tap all sides down firmly.
Measure the length, width and depth of the finished frame. Subtract 4 inches from the top of the frame. Use this shorter depth and multiply with the length and width to find the volume of soil you need to add to the frame to fill the raised bed.