The county highway engineer shall be custodian of all tools, material and machinery belonging to the road districts and to the county, except as may be otherwise provided by law.  When delivering to any road overseer the tools and machinery belonging to the district, he shall require from the overseer an inventory and receipt for all such tools and machinery, and the overseer shall be responsible for the proper care and handling of said tools and machinery, and shall see that they are properly kept when not in use, and shall account for the same to the county highway engineer.