Hello again and thank you for your reply, although I still don't have the context and background that I asked for. However, I can tell you what the law says about this and you can then apply it to the context or background of the situation.
In general, there is no expectation of privacy
in the workplace unless the employer, or a bargaining agreement, says there is. That said, certain items and locations may be protected by privacy rights. For example, restrooms and items that are clearly of a personal nature like a wallet,backpack or a purse. However, even with the personal items, if the employer gives prior notice that they are subject to search or inspection, then usually the courts will allow this intrusion into privacy based on a legitimate business reason. For example, to look for weapons or company property or company secrets.
So, in terms of the tool box, if it is being used for work, then the courts would generally not say that it is personal in nature when it is in the workplace and therefore the employer can search it. It is best though if employers make it clear in writing that there is no expectation of privacy in the workplace and what is or isn't subject to a search so that there are no conflicts over the issue. It isn't required that this be in writing, but it is the best policy.
The employee though is free to raise the issue of violation of his or her privacy rights either through the union, if there is anything that arguably applies in the BA,or by hiring an attorney to file suit. Then the court has to decide the issue based on all of the facts of the case including why the search was done, why the toolbox is in the workplace and how it is used, any notices employees have received about searches and what was found and what action was taken as a result of that, etc.
Please let me know if you need any clarification. I would be glad to assist you further if I can.