A level has a level body made of a hollow profiled section having a bottom wall whose underside forms a measuring surface and further having a top wall and sidewalls, the sidewalls connecting the bottom wall and the top wall. The level body has a window opening for receiving a horizontal vial for horizontal measurement. A securing device for mounting the horizontal vial within the level body is provided. The securing device has a vial holder, in which the horizontal vial is secured, and at least one clamping part that is movable relative to the vial holder for clamping the securing device in the level body. In the mounted state of the securing device, the at least one clamping part is supported on an inner side of the top wall and the vial holder is pressed against an inner side of the bottom wall.