Two men have begun an attempt to set a world record for the longest time spent continuously on a see-saw.
Richard March and Michael Jones started on Saturday in Twyford, Berkshire, where an unofficial record of 80 hours on the bounce was set in 1969 by Mr Jones’ father-in-law.
The pair are eating, sleeping and answering calls of nature on the giant homemade machine.
They aim to finish on Tuesday night after bouncing about 60,000 times.
The pair, who met just minutes before starting the attempt, said fatigue was the main obstacle.
Mr March said: “I’m very nervous but we’ve got plenty of people around to keep motivated.”
His fellow contender and counter-weight said: “Richard’s probably not going to hear the end of me while I’ll be chatting away to him trying to keep myself awake.”
Mr Jones’ father-in-law, David Turner, spent three months building the machine from scavenged timber, motorcycle suspension parts and a trampoline.
He said each man achieved about three hours’ sleep on Saturday night, while the other used pull-ropes to continue the see-saw’s motion.
“Obviously four days to keep awake is quite a task so what they’ll have to do is do shifts in the night,” he said.
The pair are trying to sleep in reclining car seats as they move up and down, although the machine’s toilet, in a cubicle in the centre, is stationary.
They are being joined on the see-saw by friends, working in shifts.
The record attempt is taking place in a Grade ll-listed former school to raise funds to turn it into a library.
The official Guinness World Record for the longest time spent continuously on a see-saw is 75 hours and 10 minutes, set by two women in Washington, USA, in 2004.