An aid device for mounting and/or dismantling a guide ring segment which is to be attached or is held on a support, in particular a turbine guide blade guide support of a gas turbine is disclosed. The aid device having a main body, which can be fastened releasably fastened to the guide ring segment, and having a holding device, to which a traction mechanism can be fastened releasably, wherein the holding device is configured to transmit a pulling force to the main body, which pulling force acts via the traction mechanism in an installing direction or an expelling direction of the guide ring segment.