Its mold its when your your walls get moist make sure they don't get bigger it means you have a leak in your roof!
The line where the ceiling meets the wall is called a cornice. A cornice can be set off from the ceiling with the use of cornice trim. The line where the wall meets the floor is called a baseboard.
The corner. Where the floor meets a wall. Or the ceiling meets the wall. In the window sill. In a door way.
The most common places to find cracks where the wall meets the ceiling are usually in the corners of rooms and along seams where different sections of drywall meet.
To repair a crack where the wall meets the ceiling, you can start by cleaning out the crack and removing any loose debris. Then, apply a flexible caulk or joint compound to fill in the crack. Smooth it out with a putty knife and let it dry completely. Sand the area lightly and repaint to blend it in with the rest of the wall and ceiling.
The line where a wall meets the floor is called the baseboard or skirting board. It serves to cover the joint between the wall and the floor and can also provide protection to the wall from furniture and other potential damage. The line where a wall meets the ceiling is called the crown molding or cornice. It is a decorative trim that adds visual interest to a room and can help create a finished look to the space.
bird blocks and ridge vent
An edge. A horizontal edge, to be more precise.
crown moulding
Try to position the ceiling vent so that the air washes down the exterior wall and window eliminating hot spots in the room.
The ceiling.
A ceiling partition is a track on the ceiling that may have a metal or wooden wall fitting into it. This divides a room by the ceiling support.
Non-coplanar lines. They could be parallel or skew.For example, consider yourself facing a wall in a cuboid room. Line 1 = where the floor meets the wall in front of you, Line 2 = where the ceiling meets the wall in front of you, Line 3 = where the floor meets the wall behind you. Then Lines 1, 2 and 3 are parallel but not in the same plane.OrLine 4 = where the walls to the left and behind you meet. Lines 1 and 4 are not parallel nor in the same plane: they are skew.