The device has taken out this year's National Fieldays Young Innovators award.
Hugh Jackson and Ben McColgan (pictured) at Fieldays showed their 'crankholder' – a bracket that attaches to a trailer and to the posthole borer, replacing a person.
Jackson, from a farm, says it started as a school project to invent something.
"My dad helped us come up with this idea and then we developed it from there and produced a prototype," he told Rural News. "The idea is to reduce the cost of labour by having only one person operate a posthole borer.
"Digging postholes can be dangerous and painful to the back and our product mitigates these problems."
The boys are keen to see how far they can take their idea and hope to adapt it for use with a quad or tractor.
Jackson and McColgan say their goal is to study next year at Massey or Lincoln universities.
