Doesn't matter if you don't damage it, it's still unlawful (but possibly not worth actioning). 'Trespass to property' or 'trespass to chattels' is the legal term for interfering with someone else's personal property without consent. The word trespass is more commonly used for real property (land) for general understanding, but the principle is the came - it means you're present on/touching something when you don't have consent. It has to be deliberate - not accidental; but being deliberate can be as the result of negligence (e.g. unintentional, but reckless as to the consequences).