Suikō (推敲): pushing and knocking. The Daijisen dictionary defines it as examining the words of a poem or text closely and working them over again.
The word comes from a story recorded in the Chinese work Tōshi kiji. The poet Jia Dao was writing a line about a monk at a gate under the moon. He could not decide whether the monk should push the gate or knock on it. Han Yu, a high official and a famous poet, advised him.