Draw a vertical line the full height of the wall as a guide; then hang the piece so its factory-cut edge is against the line.

One side of the strip must include the factory-cut edge of the panel, which is usually quite straight.

Start by sawing off a six-inch wide strip, one with the factory-cut edge.

Then place the saw on top of the sheet next to the strip's factory-cut edge.

The width extending beyond the factory-cut edge should exactly equal the width of the saw's base plate.

In both cases, one of the long edges must be the factory-cut edge, which is straight and smooth.

Cut off a strip approximately six inches wide that includes the factory-cut edge.

Then set the saw on top of the piece, next to the factory-cut edge.

The sawcut need not be perfect, but the strip has to include a factory-cut edge, as they are usually precisely straight.

Cut the six-inch strip freehand, approximately parallel to the factory-cut edge.