The Grappling Hook will become your best friend when starting out the game and is still very handy all the way through the game.
Be warned though, you can catapult yourself in the air and fall to your death so be careful.
Press the 'F' Button to use the Grappling Hook. Once you reach your target, the grappling hook will release. Alternatively, pressing the space bar will release the grappling hook at any time.
Currently the grappling hook is unable to 'hold' you up, only propel you in the direction of the head.