IT IS an essential item for any kilt-wearing man but, as far as a leading private school is concerned, it is too dangerous by half.
George Watson's College in Edinburgh has banned pupils from wearing sgian-dubhs inside their kilt socks.
Boys at the 8,000-a-year school have been warned to avoid bringing the short ceremonial daggers - which typically have a three-inch blade - to their sixth-year Christmas dance, because of health and safety concerns.
A letter sent to parents last week stated: "It is not essential for boys to wear either dinner suits or Highland dress, although if boys opt for the latter, a sgian-dubh should not be worn."
The school confirmed that pupils who ignore the warning will have the offending items - in use since the 17th century - confiscated.
The decision follows incidents at previous parties where sgian-dubhs were considered a safety hazard, because they had fallen out of pupils' socks while dancing or been left lying around during festivities.
Sgian-dubhs are exempt from knife legislation, because they are considered part of traditional Highland dress. However, George Watson's has decided to ban them regardless.
A spokeswoman said: "It was a decision made purely on health and safety grounds. This was a commonsense approach and pupils did not question our motives at all. However, as we have told parents, it is their responsibility to make sure that pupils comply. If they don't, sgian-dubhs will be removed at the door and another letter sent home."
However, teachers at other leading Scottish schools said they had no intention of introducing similar measures for pupils who wear kilts at parties and other social events.
Angus Macdonald, head teacher at Lomond School in Helensburgh, said: "I have some sympathy for what they are doing, but as soon as you start risk and safety analysis you are going to end up going down the George Watson's route.
"Sgian-dubhs have not caused us any problems and the vast majority issued by kilt-hire companies are harmless plastic. We have no plans to review the situation."
John Light, rector of the Edinburgh Academy, said: "We are very conscious of safety, but one has to strike a balance on issues like this. We have not had any problems with sgian-dubhs, but if Watson's has, then I suppose it was right that they addressed it."
Although pupils at Watson's face nothing more than a letter home if they break the rules, schools in other countries are not as lenient. In Michigan, America, bagpiper Jeremy Hix was disciplined for wearing a sgian-dubh to his high-school prom in 2001. He was forced to leave the prom and banned from classes for the rest of the school year.
Hix said at the time: "It's part of the formal wear for a Scottish man. It doesn't stand out when you look at it. It's sort of natural."
In 2004, when First Minister Jack McConnell announced new powers allowing the police to arrest anyone found carrying a knife, he decided to exempt the sgian-dubh because it is part of Scotland's national dress. Some campaigners, however, argued that the ceremonial daggers were sufficiently dangerous to warrant a ban.