Dry Goods
The “longest rod” listing represents the length of a rod, staff, wand, arrow, sword, or other similar item that can be placed in an empty container and still be able to fully close it.
Liquids
Hauling Vehicles
Failure DC explanation-
A vehicle has a chance of failing (breaking) if it is overloaded. The carrying weights listed are the maximum they can carry without breaking. They can be loaded up to half the listed weight without making a saving throw. If a saving throw is required the DC for the save is as indicated.
Example: A Cart can be loaded with up to 500 lbs. (half of the maximum) without having to make a save. If it is loaded with 750 lbs. a save against a DC 14 is required. [All carried weights are rounded down. 750 lbs rounds down to 700. (2 per 100 lbs) results in 2 x 7 for a DC of 14.] If the player rolls anything less than 14 on his 20 sided die, the cart fails.