Abstract: The invention relates to a gantry device (10) for use in the assembly or maintenance of heavy parts or machine components or metal parts of a travelling device. The gantry device (10) comprises two lateral bipods (11), every bipod (11) having beam-type, elongate limbs (12) and a connecting element (13) and the limbs (12) being secured to said connecting element (13) with their top ends. The limbs have four extension elements (14), an extension element (14) being arranged on a lower end of every limb (12) or support (12) or beam (12). A cross member (15) extends between the two lateral bipods (11) and is secured to every end of the cross member (15) in the corresponding connecting element (13). The device (10) further comprises a trolley with a roller, which trolley is arranged on the cross member (15) in such a manner that it can be displaced along the cross member (15) in the area between the lateral bipods (11) or horizontally moved.