Nut and line connection

A use of a nut in a leakage test of a line connection, wherein the line connection comprises:

• first and second line ends;
• the nut comprising at least one expansion region, which nut extends along a longitudinal direction, and wherein the expansion region circumferentially has one or more cutouts extending transversely and/or obliquely with respect to the longitudinal direction, wherein
• a respective length of the one or more cutouts is greater than a respective width of the one or more cutouts and wherein the length extends transversely and/or obliquely with respect to the longitudinal direction,
• the nut has a shoulder region, a threaded region and a middle region disposed between the shoulder region and the threaded region, wherein the shoulder region and the middle region are unthreaded,
• the expansion region is arranged in the unthreaded middle region and not in the shoulder region and threaded region, or the expansion region is arranged in the unthreaded middle region and in the threaded region but not in the shoulder region,
• the first and second line ends are connected via the nut,
• the first line end has a first sealing surface,
• the second line end has a second sealing surface,
• the expansion region of the nut, in a screwed-together state, is positioned at least between the first sealing surface and the second sealing surface.