The chalk line (marking cord ) is an aid to create straight lines on walls. Usually it is used in interior construction , in wood construction and in building the building services. Chalk lines are, for example, 30 m long.
Today's chalk lines are housed in a housing in which the thread is wound. The case is filled with a colored powdered chalk. When rolling up and pulling out the cord, it is smeared with chalk. So that the chalk powder does not trickle out of the housing, the hole through which the cord is led out is hardly larger than the cord diameter.
For this reason, the line must be handled with care; Knots or hardened plaster or mortar residues would prevent it from being rolled up again and render the chalk line unusable. For the same reason, the device should not be wet or the cord should be rolled up when wet.
To apply a line, the ends of the cord are carefully held against the area to be marked and the cord is taut. The housing can also be used as a solder . If you pull the cord a little away from the surface and let go of it, it hits the surface and the adhering chalk dust marks a straight line.