A driver was told by a judge to buy a £1 ice scraper instead of keeping a knife in his car to do the job.
Michael Yates's use of the tool left him with a suspended jail sentence and having to do 200 hours unpaid work.
As he appeared in court, Recorder Sandeep Kainth said: "I have never heard of anyone using a knife.
"What is the explanation not to go to Halford's to get a window scraper? You could go to the one pound shop to buy a windscreen scraper.
"It really beggars belief that you are using a knife for this in the current climate," he told Yates, 30, of Andover Road, Bestwood.
Nottingham Crown Court heard Yates had appeared before magistrates who convicted him of having a blade in public near his home on February 15.
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Abigail Hill, prosecuting, said he was in a car which police officers pulled over the searched. In the driver's door pocket, they found a kitchen knife with a nine-centimetre blade.
Miss Hill told the court: "He admitted possession of the knife.
"He said he used it as an ice scraper, to de-ice the windscreen," said Miss Hill. It was held together by an elastic band.
The court heard Yates had 49 previous offences on his record. At the time, he was under a four-week prison sentence, suspended for a year, which was imposed because he had escaped from Sudbury Open Prison, south Derbyshire.
As a result of the new offence, the recorder left this prison term in place for an extra two months. He gave Yates a four-month jail term, suspended for a year, for the knife crime and said that he must also do 200 hours unpaid work.
Emma Coverley, mitigating, described Yates as "a family man" who had been working as a van driver after being released from prison.
When asked about him using a knife to clear his windscreen, Miss Coverley added: "Any explanation I give would not be satisfactory."
A probation report said he has been doing well since his last prison term. Tests showed he has stopped taking drugs.
