How to Make Square Corners

Once you know where the bed will go, line up pressure-treated lumber to mark the edge. You can use any size. The number of boards you need will depend on the size of your bed and the length of the material.

Tip: If you need to make a square corner for a paving project or fence installation, build batter boards during this step. A batter board is a temporary frame that consists of horizontal boards nailed to posts.

Mark a straight line parallel to the laid-out edge of your bed. Measure 12 to 18 inches from the end of the board closest to the corner with a measuring tape. Use a mallet to pound a stake into the ground at this point. Call this Stake A.

Move to the other end of the board. Again, drive a stake 12 to 18 inches from the end with a mallet. This is Stake B.

Wrap the mason's line around Stake B until it overlaps itself. Cinch the line tightly and wrap the line around a second time to create a second overlap.

Run the mason's line from Stake B to Stake A. To secure it, wrap the mason's line around the stake, cinch and overlap again.

Place a second piece of lumber to form the other edge of your bed, and refer to a laser level to make it as straight as possible.

Measure out 12 to 18 inches from Stake A, moving away from your project. Drive Stake C into the ground at this point.

Move to the other end of the board you positioned in this step, measure 12 to 18 inches and pound a stake into the ground. This stake is Stake D.

Run the mason's line from Stake A to Stake C. Overlap the line once around Stake C, cinch and wrap a second time.

Now, continue to run the mason's line from Stake C to Stake D. The line will cross over the line you ran in Step 3.

Walk back to the corner of the project and locate the point where the lines crisscross. This is the layout for your corner.

At this point, the corner will be close to 90 degrees. You will adjust it to get a perfectly square corner in the next steps.

The simplest way to square a corner is to use the 3-4-5 method from the Pythagorean theorem. It states that the sum of the squares of the two legs of a right triangle will equal the square of the long side, called the hypotenuse. Based on the theorem, a triangle with legs that measure 3 feet and 4 feet will have a 5-foot hypotenuse.

To begin with the 3-4-5 method, measure 4 feet from the corner along the line that runs from Stake A to Stake B. Use a small piece of masking tape to mark the point. This point is Point A. Now, measure 3 feet from the corner along the line that runs from Stake C to Stake D. Mark the point with a small piece of masking tape and refer to this as Point B.

Tip: Although you can do the remaining steps on your own, an assistant can simplify the work. Have the other person hold the measuring tape, so you can focus on placing the tape at the exact spot.

Measure the distance from Point A to Point B. Keep the measuring tape as flat as possible. Ensure that you read the same side you did in Step 7.

If the distance is exactly 5 feet, your corner is square, and you can proceed to Step 10. Otherwise, continue to Step 9.

If the distance from Point A to Point B is less than 5 feet, move Stake D outward. If the measurement is more than 5 feet, shift Stake D inward.

Refer to a laser level as you position Stake D. Once you feel satisfied, use a mallet to drive the stake back into the ground.

Measure from Point A to Point B again. Continue to adjust until the length is exactly 5 feet.

Now that you have a square corner, tie plumb bobs at the tape marks. Use powdered chalk to mark the corner. Repeat this process to square the remaining corners of your garden bed.