Jamieson, Fausset and Brown on 1 Kings 7:27-39

27-39. he made ten bases of brass--These were trucks or four-wheeled carriages, for the support and conveyance of the lavers. The description of their structure shows that they were elegantly fitted up and skilfully adapted to their purpose. They stood, not on the axles, but on four rests attached to the axles, so that the figured sides were considerably raised above the wheels. They were all exactly alike in form and size. The lavers which were borne upon them were vessels capable each of holding three hundred gallons of water, upwards of a ton weight. The whole, when full of water, would be no less than two tons [Napier].