ride herd on someone/something
ride herd on (someone or something)
To closely observe or monitor someone or something to supervise or maintain control. An allusion to a cowboy riding on his horse to keep a herd of cattle in order. We want the groups of students to work independently, but we should have a teacher riding herd on each one to make sure they stay focused. Being a camp counselor is a lot of fun, but having to ride herd on a bunch of kids for two weeks at a time can be exhausting.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
ride herd on someone/somethingAMERICAN
If someone rides herd on other people or their actions, they control them. It's his job to ride herd on organizers to keep them on schedule. Note: People sometimes use over instead of on. The ideal situation is one where everyone feels responsible and no one person has to ride herd over the others. Note: Originally, `riding herd' involved patrolling on horseback around a herd of animals, in order to make sure none of them wandered away.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012