A storage yard used to obtain and deliver a good is typically set to "get 1/4" of the good. For example, a storage yard might "get 1/4" clay and deliver it to nearby potters. But the distribution can be doubled by putting more than 1600 of an "inert" good in the storage yard and setting it to "get maximum". In the above example, the storage yard would use 2 cart pushers to obtain and deliver clay if the storage yard contained 2400 grain and was set to "get maximum" (or "get 3/4") clay.
The technique also works if the storage yard is full of "other" goods. This should be especially useful when the storage yard is distributing river imports and has a road connection to the dock. For example, I'm designing a Baki with all roads connected, and a lot of papyrus will be imported by river. A single storage yard near the dock will accept papyrus, and several other storage yards that are filled with figs (or something similar) will "get" papyrus and deliver it to schools and libraries. Not only will the papyrus distributing storage yards send out 2 cart pushers, but the dockers will only be able to deliver papyrus to the nearby storage yard.