Is there a general term for an inventory item that is taken from over time?

Bulk goods is one way to describe items that are transported unpackaged in large quantities, which are typically bought in smaller, measured quantities. For example, in the Bulk Foods section of a grocery store, you'll find large containers of cereals, grains, granola, etc., from which shoppers fill a smaller container that is then priced by weight. Instead of buying a 1, 3, or 5 pound bag of rice by the unit, you can purchase any quantity by measure.

Most items I've seen described as bulk goods are typically sold by weight, so it might not be the best fit for rope or gasoline, which are sold by length and volume, respectively.