This week in the French conversation group one of the things that came up was the expression “as flat as a pancake” or the slightly ruder version, “as flat as a witch’s tit”. This was being used to describe the flatness of beer. The only equivalent we could find in French was “completement plat” (completely flat), though I’ve since found a couple of others: “plat comme une limande” (‘flat like a dab*’) [source], and “plat comme une lamelle” (‘flat like a sliver/thin slice’) [source].
Other variations of the English phrases I’ve found include “as flat as a board”, “as flat as an ironing board” and “as flat as a trencher”.
What other flat things might appear in this expression?
Are there interesting equivalents of this phrase in other languages?
*Dab = a species of small flat-fish, Pleuronectes limanda, similar to a flounder [source]