room

in a smoke-filled room (of political bargaining or decision-making) conducted privately by a small group of influential people rather than more openly or democratically.

☞ This expression comes from a 1920 news report about the selection of the Republican presidential candidate: '[Warren] Harding of Ohio was chosen by a group of men in a smoke-filled room'.

no (or not) room to swing a cat used in reference to a very confined space. humorous

☞ The cat in this expression is probably a 'cat-o'-nine-tails', a form of whip with nine knotted cords. In former times these whips were used to flog wrongdoers, especially at sea.

room at the top opportunity to join an elite or the top ranks of a profession.

☞ The expression is attributed to the American politician Daniel Webster (1782–1852), who was cautioned against attempting to enter the overcrowded legal profession and is said to have replied: 'There is always room at the top'.