Do you know that some special buildings, like Water Tower, Ice, Coal, and Iron Units, need to be repaired with tool boxes / engineering kits after their limit is exhausted?
Tool boxes are quite rare in the world of Klondike, but an old Inuit knows all the ways of getting them:

- win them in marathons and pearl hunts;
- get them as a reward completing timed quests;

- buy them in the Trade Company's shop with your hard earned Trade Company's bills;
- obtain them together with other items in a special pack our Mayor composed;

That's all at the moment, but the Inuit promised to think about more ways to obtain the precious engineering kits ;)