What it do, I'm on the block posted up like a mailbox
Posted on the block usually means standing around on the sidewalk. Drug dealers stand on sidewalks so it is easy to find them. Mailboxes also stand on sidewalks but are less likely to be drug dealers.
To help improve the meaning of these lyrics, visit “Sittin' Sidewayz” by Paul Wall (Ft. Big Pokey) Lyrics and leave a comment on the lyrics box