Hardboard siding is a product manufactured from cement and fibres. Prone to failure when not installed correctly, the siding is pre-coated with primer to reduce water saturation. The ends of hardboard siding must be coated with primer after cutting to waterproof them and avoid damage to the siding. In addition, caulk all cuts and joints after installation and protect the siding with a high-quality paint to seal it against moisture damage.
Place the hardboard siding on a stable work surface.
Use a tape measure to determine the size of the piece needed. Measure the siding from the end to the right distance for the cut. Mark the location with a pencil or fine-tipped marker.
Place one edge of the square against the mark and the other edge of the square flush with the edge of the siding. Draw a straight line along the edge of the square in line with the cutting mark.
Cut the hardboard siding with a circular or hand saw. If cutting with a circular saw, cut with the siding's face down against the work surface. If cutting with a hand saw, cut with the siding face up, away from the work surface.
Coat the cut end of the siding using a paintbrush and high-quality exterior primer and allow to dry before installation.
Plan multiple cuts at one time and paint with high-quality exterior primer to save time.