"Pull" vs. "Push" agent flow protocol

AnyLogic supports two alternative agent flow protocols for Process Modeling Library flowcharts. 

The following blocks support “Pull” protocol and also provide "Push" protocol as an option: Source, Enter, Delay, Pickup, Dropoff, Seize, Batch, Unbatch, Combine. Selecting the advanced Forced pushing option, you turn the Push protocol on for the block: