Answer: The meaning of bolt in the sentence is (Definition 3) "n. a bar that slides to lock something".
Explanation: The word "bolt" can have different meanings; however, in the sentence provided ("Please make sure you latch the bolt on the window when yo close it tonight") "bolt" is used as a noun and it makes reference to a bar on a door or window that slides to lock this door or window. The words 'window' and 'latch', which means to close something, allow the reader to infer that the meaning of 'bolt' is the one included in definition 3.