They are the most famous fences in the world and they have to be ready on time.
The 16 obstacles at Aintree are being made perfect for next week's Grand National by groundsmen, despite the poor weather making their job that bit more difficult.
Head groundsman Mark Aynsley is confident his men can deliver, and the team continue to weave 18 lorry loads of Cumbrian spruce into shape.
He said: "The fences will be ready by Monday or Tuesday and will have been checked at least three times to ensure they meet the standard.
"At this time of year the team is up against the weather. It doesn't matter how bad it gets - wind, rain or snow - they have to be out there building those fences."
The biggest challenge is The Chair, fence number 15, which stands at a whopping 5'2" tall and takes about a day-and-a- half to build.
It takes three weeks' work to construct all the fences in time for the three-day festival, which starts next Thursday.
"It's hard work but secretly I do think they enjoy it," Mr Aynsley said of his team, which includes seven ground staff, two green keepers and a gardener.
"There isn't a course in the world that does this like we do. The team appreciate the gravitas of their work.
"Then they will just stand back and watch the horses wreck all their hard work in about three seconds flat."
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