Taken directly from here.
Knives should be considered as a tool and treated as such. Those who are going to use them should get training for their use, as you would for a saw or an axe. Knives are an offensive weapon so great care should be taken when dealing with them. When undertaking training at the Scout HQ, knives should be taken to and from Scouts by an adult. When taking a knife to camp, they should be securely stowed in the middle of the rucksack or bag.
If you consider a knife as a tool, then you should use the appropriate tool for the job. The vast majority of Scout use will only require the use of a pen or clasp knife, the cutting of string, cooking or whittling. Where you have a larger task, such as splitting wood, a larger knife such as a sheath knife may be appropriate. If you relate this to axes, you would not use a hand axe to fell a tree, nor a felling axe to split wood.
There is an issue with regard to clasp knives and lock knives. A lock knife is one where the blade stays open unless some mechanism is used to close the blade. In the eyes of the Law, this is more of an offensive weapon than a standard clasp knife because of this multiple action. From a safety point of view, a lock knife can not fold onto the users fingers and may be better.
The carriage of knives is also to be considered. If a knife is considered as a tool, you would only really carry the knife when there is an expectation to use the tool, after all, you wouldn't carry an axe around a campsite on the off chance of coming across some wood to chop. Therefore, knives when not being used should be stowed away until such time as they are needed. Legally, you are not allowed to carry a knife in a public place without lawful authority or reasonable excuse. A campsite, which may technically be private property as it is owned by a District or County, is considered as public property because of its use. Knives should not be carried unless they are going to be used, and should be put away when not in use.