Abstract: An apparatus and method for providing a drilling rig substructure on a fixed platform which includes the transfer of the drilling rig substructure from a movable jack-up type rig to an adjacent, fixed oil platform. The method provided utilizes a conventional type jack-up rig which includes a barge mounted telescopically on a plurality of structural support legs. A substructure, containing the entire apparatus for drilling or reworking an oil or gas well, connected to an associated bridge and skid mat, are connectably housed on the barge portion of the jack-up rig. The barge is elevated to the approximate level of the fixed platform to which the drilling apparatus is to be transferred. The substructure, bridge and skid mat are slid from the barge towards the surface of the fixed platform to a degree which leaves the substructure and associated drilling apparatus on the barge portion of the jack-up rig.