To fix the bar, you can use small metal screws. Take measurements and prepare the details of the slopes of drywall. Then sketch the adhesive mixture on the primed surfaces of the old slopes. After that, we start the end of the side sloping details into the profile and press the drywall to the adhesive mass. Using a square, set a vertical side slope from the right angle. To correctly install the slope, you can slightly pat the hand over the plasterboard part. Similarly, we install another side slope. At the top of the window we mark the lines along which the upper slope will be mounted. On these lines we screw the profile to the side slopes. It turns out that we put the upper part of drywall in three slats, screwed to the side slopes and frame. That’s all — the slopes are ready! If drywall protrudes behind the walls, draw the desired lines, and then cut off the protruding material.