Unlatch \Un*latch"\, v. i. [imp. & p. p. {Unlatched}; p. pr. & vb. n. {Unlatching}.] [1st un- + latch.] To open or loose by lifting the latch; as, to unlatch a door.
Then, you must push down a rammed-shut window, reach over the open pane and unlatch the door with the outside handle.