For technical or purely aesthetic reasons, it is common to stop a false ceiling vertically or at an angle.
Fallout at right angles
Above the horizontal plate, locate the location of the lift to achieve by using a spirit level.
After tracing the pins to the chalk line, cut an angle to the correct length and then fix it to the ceiling.
Measure the total height (plate thickness included), then cut a piece of plate and screw it into the corner and into the fur.
Fix an angle flush with the ceiling.
The end fur must be partially visible to screw the connection plate.
Put in place the plasterboard connection.
Screw it in the fur and in the angle iron, applying it well against the wall.
Plan the angle formed by the plates with the cutter or the plaster grater to adjust them better.
Finish the ridge with an armed band embedded in the plaster.