Jackup - A deck with legs that can be jacked up or down. During operations, the legs rest on the sea-bed. When the rig is moved, the legs are retracted, leaving the rig floating. A jackup has normally no propulsion machinery of its own.

JONES ACT- Merchant Marine Act of 1920, Section 27, requiring that all U.S. domestic waterborne trade be carried by U.S.-flag, U.S.-built, and U.S.-manned vessels.