nail down
     v 1: succeed in obtaining a position; "He nailed down a spot at
          Harvard" [syn: {nail}, {peg}]
     2: define clearly; "I cannot narrow down the rules for this
        game" [syn: {pin down}, {peg down}, {narrow down}, {narrow},
         {specify}]
     3: make final; put the last touches on; put into final form;
        "let's finalize the proposal" [syn: {finalize}, {finalise},
         {settle}]
Source: WordNet® 2.0