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.

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