- 1). Check the squareness of a 90-degree cut board by placing the combination square so that the long ruler-like side is resting lengthwise across the cut. Position the 90-degree "handle" of the combination square along the uncut side of the board. The uncut side is assumed to be relatively square from the lumber company. With both the 90-degree handle flush against the side of the board, the cut across the board can be checked.
- 2). Adjust the ruler-like slide and position the combination square on a piece of trim where a miter cut has been roughly drawn. Align the ruler-like slide with the length of the wood and the 45-degree side of the handle to match the direction of the miter. Correct the rough drawn mark by drawing the line accurately with your pencil.
- 3). Place the combination square so that the ruler-type slide lays across the board. Position your pencil to your desired length and bring the slide to the pencil keeping the handle firm along the side of the board. This will allow you to make clean 90-degree cutting lines.
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