Toolboxes boost a certain parameter of your spare part depending on the stars the toolbox have,the more the stars,the more points added. You can obtain a Toolbox by opening Supply Boxes. The more Toolboxes you fuse into the part, the more the fuse costs.
Applying toolboxes to chassis's increase in cost the more toolboxes are applied.
The star level for toolboxes also increases the cost, but also increase the boost of health and attack.
Power toolboxes will always give 1 energy no matter the star level, but will continue to cost more the higher the star level. This may cause players to camp for low leveled power toolboxes.