What device did Mama use to keep Jumper away from the corn in chapter 12 of Old Yeller?

There is a terrible drought and Jumper, the family's mule, does not want to eat the dried-up grass. He repeatedly jumps the fence that corrals him, and he eats the corn that has not yet been gathered. The family cannot let this go on because they need corn to make bread for the winter. The mother finds a clever way to keep Jumper from eating the corn by tying a "drag" to him. Specifically, she attaches a heavy piece of wood to his right forefoot with a rope. The wood is heavy, but with effort, Jumper can still move enough to get his necessary food and drink. The wood is too heavy, however, for him to be able to jump the fence; therefore, the corn is saved.