Mark a clear square line on a board before a project.

A neat pencil line is a useful first step for a small woodworking project. A combination square helps you draw a line at 90 degrees to a board’s reference edge instead of guessing by eye. Practice on a clean scrap of new, untreated lumber; this exercise is only about measuring and marking.

What you’ll need

• Combination square
• Metal tape measure
• Sharp pencil
• Clean scrap board with a straight reference edge
• Stable workbench
• Clamp if needed

Take it step by step

1. Set the board flat on a stable surface. Check that the reference edge is straight and free of chips or debris that could prevent the square’s head from seating properly.
2. Measure from your chosen starting end and make a small pencil tick at the desired length. Read the tape straight on and use the same starting point for a second check.
3. Adjust the square’s ruler so it reaches across the board, then lock it according to the tool instructions. Use the head’s 90-degree face for a square line.
4. Hold that face firmly against the reference edge. Slide the tool until the ruler meets your pencil tick, keeping the head fully seated rather than tilted.
5. Draw a thin line along the ruler with light pencil pressure. Recheck the measured location and the head’s contact with the edge before lifting the tool away.
6. If you later plan a cut, identify which part you intend to keep and label the waste side. A saw removes material, so the layout line and the cutting method must be considered separately.

When to ask for help

Ask an experienced woodworker for help if the square is damaged, its ruler slips when locked, the board edge is irregular, or repeated checks disagree. Resolve the layout before starting any cutting.