How to Install Smoke Alarms on Cathedral Ceilings

Twist the top of the smoke detector off the base with a counterclockwise motion. Insert a battery into the battery compartment. Twist the top back on the base with a clockwise motion.

Place the A-frame ladder, also known as a "telescoping ladder" beneath one of the angled beams in the cathedral-type ceiling.

Place the smoke detector's mounting plate against the beam, just before it meets the ceiling, on the side closest to the center of the ceiling. Mount the plate to the beam with wood screws using a Phillips screwdriver.

Twist the smoke detector onto the mounting plate with a clockwise motion; if one of the detector's side vents doesn't face down towards the floor, twist the detector off the plate and reorient it so it will once twisted back on.

Press the "Test/Reset" button on the side of the smoke detector for a second to verify that it is working. Return the ladder to the place it was rented from.