A guide structure is provided for guiding deployment of a pipeline from a hang-off structure through an opening in a vessel during a J-lay operation. The guide structure comprises a port-side guide assembly and a starboard-side guide assembly for engaging and guiding the pipeline below the hang-off structure, wherein the port and star-board-side guide assemblies are independently moveable to engage and guide the pipeline. The guide assemblies may be mounted to traverse on rails provided within the opening.
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