Measure the cutout you need to make on the wood flooring plank. Put the wood plank in place to make marks if possible. For example, on a floor vent, put the wood plank in position so you can determine the location of the cuts for the vent notch. Measure the depth of the cutout needed between those two end points to finish the notch.
Mark the cutout on the piece of wood flooring using a wood pencil. Measure the cutout onto the board and draw with the pencil to outline the notch.
Drill a hole at the corners of the notches. The drilled holes make it easier to cut the 90-degree angles, which are difficult to do with a jigsaw. Place the drill hole so it stays inside the cutout area. If it goes past the line into the area of the wood plank, you will have a gap or larger cutout than needed.
Fit the jigsaw with a wood cutting blade. Place masking tape over the cutting lines to protect the wood as you cut.
Clamp the board to the work surface to hold it securely in place while cutting. Cut along the marked lines slowly to follow the lines and get straight cuts.
Put your flooring plank in place to determine if the cuts are correct. Make adjustments to the cuts as needed to fit properly.