Drive a stake at the beginning of where you visualize your fence. Walk the length of the imaginary fence line and sink another stake at the end. If your fence will have more than one side, repeat for each. Long stretches of fence benefit from more than one stake to mark the run.
Tie the end of a ball of twine around the first stake. Wrap the string around each stake, in turn, tying it off at the last stake. The stakes and string form a straight line to follow so that your fence won't end up crooked or wavy.
Sort through your pallets to ensure each is sturdy. Discard or repair those with cracked or loose boards. The center, which comprises the pallet frame, must consist of unbroken boards.
Cut 4-by-4-inch boards, one for each pallet section used, to the desired height for use as fence posts. Allow for the height of the pallets, at least 2 feet to sink beneath the ground for stability and a few inches clearance between the ground and fence. This prevents the fence from resting in standing water and small amounts of snow. Add a few extra inches if you want the post to extend above the fence.
Remove the boards from one side of the pallet. Use a claw hammer or pry bar and work carefully to avoid damaging the pallet. When complete, you have three horizontal boards, comprising the inner pallet frame, topped with the vertical boards on one side.
Add the pallet boards using one of two methods: Nail into place, even width and between the existing boards on the front of the pallet. This creates a near solid facing, which works well for privacy. Or attach the boards on the side from which they were removed but stagger them so that wherever there is an opening between boards on one side, it is covered by a board on the opposite side, forming a more traditional privacy fence. Leave the pallet as is, without modifications, for an old-fashioned picket fence appearance.
Shape one end of the pallet's vertical boards according to the look you want. Use a jig saw to make each board end pointed, rounded or trace a template design across the boards to shape the entire fence section formed by each pallet. For this effect, cut each board slightly shorter and at an angle until you reach the middle board, from which you begin to gain height again. This creates a rolling, U-shaped effect.
Paint or stain all of the 4-by-4 support posts along with each pallet section. Alternatively, use a waterproofing sealer and retain the look of natural wood. You want to ensure the wood is durable when exposed to the elements outside.
Dig the first two post holes, starting where your first stake indicates, using a post hole digger or shovel. Make the holes slightly deeper and wider than necessary and space them the width of your pallet apart. A 4-foot-long pallet requires posts every 4 feet.
Line the holes with a small amount of gravel and add concrete, if desired, for extra sturdiness. Insert the end of a post and fill around the posts with dirt. Tamp the dirt down to ensure the post is secure.
Hold the beginning pallet section up to the posts and elevate off the ground as desired. Make sure the section is positioned appropriately. A solid pallet may present the inner structural boards toward your property and the boards outward, for example. If using a staggered privacy pallet design or a one-faced pallet design, ensure that the vertical end boards, which extend slightly past the pallet frame, overlap the post to allow you to nail it to the post.
Secure the fence section in place, using either galvanized nails or screws. Space the attachments along the board, using at least two at the top and two at the bottom. Leave half of the post exposed on the second post to allow you to attach the next fence section. Work the length of the fence, placing posts and securing fence sections similarly.