to work hard.

You're going to have to knuckle down to improve your grades if you want to get into a good college.

Volunteers really knuckled down and cleaned up the town after the storm.

• have designs on something
• have dibs on
• have dibs on something
• have done more something than has had hot dinners
• have done more something than someone has had hot dinners
• have done more than has had hot dinners
• have done more than someone has had hot dinners
• have [done/seen/had etc.] more something than has had hot dinners
• have [done/seen/had etc.] more something than someone has had hot dinners
• have [done/seen/had etc.] more than has had hot dinners
• have [done/seen/had etc.] more than someone has had hot dinners
• have down on like a ton of bricks
• have down on you like a ton of bricks
• have down pat
• have down to a fine art
• have down to a science
• have ducks in a row
• have ear
• have ear to the ground
• have egg on face
• have egg on your face
• have end away
• have eye on
• have eye on someone
• have eye on something