Every worker has a backpack, where he stores raw materials, and tools. The capacity of the backpack is limited to 30 kg and 8 slots. So make sure to pack wisely. As well as the backpack, the worker can carry one tool in each hand and drive one vehicle. Click on the Backpack tab to learn what raw materials and tools the worker is carrying or to move some stuff from the backpack or put something in it.
If you want to add more slots into your backpack, upgrade your backpack. The price of one slot is formed based on the price of plot rent.