Draw straight lines with a string

When painting or wallpapering walls, it is often necessary to mark a horizontal line on them. Two people can easily draw such a line with a string saturated with dry color pigment. A string, well lubricated with dust, is placed on the points marked on the wall, pulls it hard, and then lightly pulls away from the wall and lets go. When returning to the initial position, it will return a trace on the wall in the form of a perfectly straight line connecting points.