If the brother of a married man who died childless fails to have sex with his dead brother's wife, what must the wife do?

Take off her brother-in-law's shoe and spit in his face

And if the man like not to take his brother's wife, then let his brother's wife go up to the gate unto the elders, and say, My husband's brother refuseth to raise up unto his brother a name in Israel, he will not perform the duty of my husband's brother. ...

Then shall his brother's wife come unto him in the presence of the elders, and loose his shoe from off his foot, and spit in his face. Deuteronomy 25:7-9