flower pot
n.— «The “flower pot” was a steel container that was laid on the concrete slipway into which the ends of wooden poles were placed. Attached to the poles were “thwarts” (horizontal beams), along which planks were laid and acted as platforms for the shipyard men.» —“Getting Hooked On Slang Used In Golden Days Of The Shipyard” by Charlie Warmington News Letter (Belfast, Ireland) Dec. 22, 2005. (source: Double-Tongued Dictionary)