Things You'll Need
Miter saw or hand saw
Landscape timbers are made from naturally rot-resistant or pressure-treated wood. Typically used to build retaining walls and raised gardens, they're simple to work with and add a soft, neutral contrast to plants and blossoms. If you want to build a circular raised garden, you'll need to cut them at the same angle so they form a circle when laid end-to-end.
Measure the building site with a tape measure. Decide on how many sides the raised garden will have. It must have at least five sides to have a circular rather than square or triangular shape. Note that the more sides you have, the more timbers you will use and the closer the form will be to resembling a circle.
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Calculate the angle you must cut on each end of every timber piece. There are 360 degrees in a circle. Divide this by the number of sides your structure will have. For instance, a hexagon has six sides, so each side should equal 60 degrees. A typical straight cut is 90 degrees. Subtract 60 degrees from 90 degrees. In order to create a 60-degree angle, cut each end at a 30-degree angle.
Place an adjustable carpenter's square at the end of the first timber. Use a pencil to mark the 30-degree angle across the outer corner. Repeat this step on the corners of each length of timber.
Cut each timber along the cut line. A miter saw allows you to concentrate on cutting a straight, clean line across the pencil mark. If you only have a handsaw, continue the pencil line around each side of the timber so you can check that the line is straight as you cut. Wear safety glasses and ear plugs when working with an electric saw. Rub sandpaper over each end to smooth the ends.
Piece the bottom course of timbers together to check that they match up. Dry-lay each piece on flat grass so the 60-degree angles face up. Each piece will have a short and long side. Place the short sides toward the inside so the ends fit flush together to form a hexagon.