Abstract: A skidbase 16 and a drilling structure 18 are adapted for transfer between a jack-up platform 12 and a fixed platform 14. The jack-up platform 12 is moved into position adjacent the fixed platform 14 and raised to a height aligned with the fixed platform 14. The skidbase 16 is then transferred onto the fixed platform 14 to provide a base on which the drilling structure 18 is next placed. The jack-up platform 12 is raised to a vertical height aligned with the skidbase 16. To ensure proper location of the top surface of the jack-up platform 12 relative to the skidbase 16, a connection means 47 automatically engages and aligns the jack-up platform 12 with the skidbase 16 so that skid rails 32, 44 located on the deck of the jack-up platform 12 and on a top surface of the skidbase 16 are positioned a precise distance apart and at the same vertical height. The drilling structure 18 is then skidded onto the skidbase 16 so that drilling operations may be performed from the fixed platform 14.