The blinds in our living room are raised ever so slightly on the window closest to the door. Our dog gets upset whenever one of us leaves the house. He's fine when both of us leave, though.
He has now figured out that we have push up blinds, so whenever one of us leaves he nudges the blinds up with his snout and looks out at us. The look is usually accompanied by barking. He can also watch our return.
If we had blinds that raised and lowered with a string, I'm sure he would figure out how to wrap it around his paw or grab it in his mouth and pull.