Jamieson, Fausset and Brown on Ruth 4:7-8

7-8. a man plucked off his shoe--Where the kinsman refused to perform his duty to the family of his deceased relation, the widow was directed to pull off the shoe with some attendant circumstances of contemptuous disdain. But, as in this case, there was no refusal, the usual ignominy was spared; and the plucking off the shoe, the only ceremony observed, was a pledge of the transaction being completed.