Adjustment device for adjusting a guide rail in an elevator system, comprising at least one elevator shaft, wherein the adjustment device comprises: - at least one perpendicular; - at least one frame comprising a first segment for abutment against the guide rail and a second segment arranged perpendicular to the first segment; - a first measuring scale for detecting a position of the guide rail with respect to the at least one perpendicular in a first spatial direction, wherein the first measuring scale is arranged at the second segment of the frame; - a second measuring scale for detecting a position of the guide rail with respect to the at least one perpendicular in a second spatial direction, characterized in that the adjustment device further comprises - a try square displaceable at the second segment; - a power source; and - a signal transmitter, wherein the signal transmitter is arranged to emit a visual and/or acoustic signal when the try square is in contact with the perpendicular, wherein the signal transmitter is connected to the perpendicular via a first cable connection and is connected to the try square via a second cable connection, wherein the power source, the signal transmitter, the try square and the perpendicular are electrically connected in such a way that they form an open circuit and that the circuit is closed when the try square and the perpendicular are in contact. wherein the adjustment device comprises: - at least one perpendicular; - at least one frame comprising a first segment for abutment against the guide rail and a second segment arranged perpendicular to the first segment; - a first measuring scale for detecting a position of the guide rail with respect to the at least one perpendicular in a first spatial direction, wherein the first measuring scale is arranged at the second segment of the frame; - a second measuring scale for detecting a position of the guide rail with respect to the at least one perpendicular in a second spatial direction, - at least one perpendicular; - at least one frame comprising a first segment for abutment against the guide rail and a second segment arranged perpendicular to the first segment; - a first measuring scale for detecting a position of the guide rail with respect to the at least one perpendicular in a first spatial direction, wherein the first measuring scale is arranged at the second segment of the frame; - a second measuring scale for detecting a position of the guide rail with respect to the at least one perpendicular in a second spatial direction, characterized in that the adjustment device further comprises - a try square displaceable at the second segment; - a power source; and - a signal transmitter, wherein - a try square displaceable at the second segment; - a power source; and - a signal transmitter, wherein the signal transmitter is arranged to emit a visual and/or acoustic signal when the try square is in contact with the perpendicular, wherein the signal transmitter is connected to the perpendicular via a first cable connection and is connected to the try square via a second cable connection, wherein the power source, the signal transmitter, the try square and the perpendicular are electrically connected in such a way that they form an open circuit and that the circuit is closed when the try square and the perpendicular are in contact.