nail down (someone or something)
to make certain or sure of something
I am trying to nail down the exact time that the meeting will begin.
Rules to play Bungee Jumping
Mind Over Splatter
Although the mask of bravado I wore before my jump disintegrated as soon as I stepped onto the bungee platform, it did ensure that my mind stayed well and truly off the adventure at hand until it could be ignored no longer. Not everyone is this fortunate, however; the nights preceding a bungee jump for many are sleepless and drenched in sweat.
Being able to brag about conquering one of the worlds tallest bungee jumps was the incentive I used to manipulate my thoughts beforehand, staving off dread and focussing instead on what Id be able to tell my friends when I got back from New Zealand. Its the same reason I would gladly do another bungee jump one day, but only if it was even taller than the Nevis Bungy.