Use your tape measure and ruler to draw a square in the area you intend to add the vent. The hole should be the size of the vent not including the flanges, or strips of metal, that surround the vent. The flanges will sit flat on the roof.
Make sure that the roof and any slide-outs are fully extended before drilling a hole in one of the corners of the square. Use a large bit and drill the holes. Make sure that the bit is positioned so that the hole is drilled to the inside of the line with only its edge touching. Begin cutting the square with the saw. Cut along the rest of the lines and remove the section of roof.
Line the outside of the hole on with silicon caulk then press the vent down into the caulk. Wipe excess caulk away with a damp rag but be sure to leave enough caulk that a proper seal is formed. If in doubt, it is always better to leave more than is necessary.
Use the screws provided with the vent and a screw driver or drill to fasten the vent to your trailer's roof. Make sure not to over-tighten; doing so could bend the vent flanges and allow water to seep in.
