A double barline consists of two thin, parallel, closely spaced vertical lines with identical thickness that pass through, and also usually between, all staves. They are commonly used to separate different sections of a work and emphasize changes in time signature, tempo, and key signature. Double barlines are similar to single barlines in appearance except that there are two lines instead of one. They are usually placed at the end of a measure, but if used mid-measure, both lines are dotted instead of solid. End barlines also consist of two parallel, closely spaced vertical lines but differ from ordinary double barlines in that the second line is thicker than the first.