Do you understand me? / You know what I mean? / You follow?
Checks that the listener is following what you're saying. More direct than ¿sabes? but equally common. Can sound impatient if overused.
It's complicated, but that's how it is. You know what I mean?
It's not that I don't want to, it's that I can't. Do you follow?
—Do you understand me? —Yes, I understand you perfectly.