Hookshot Jump is a 3DS exclusive trick used to shoot upward to extreme heights.
To perform a Hookshot Jump:
Equip the Hookshot/Longshot and either the Iron or Hover boots.
Stand by a surface that the Hookshot will grab and hold the Hookshot.
Look up and then let go of the circle pad, while Link is returning to his neutral position, switch boots, this method is also known as Inverted Hookshot Jump.
More height can be gained off of an Inverted Hookshot Jump by aiming a bit higher than Link's head.
Walls/Edges can be grabbed out of a Hookshot Jump.
Normally you can't do an Inverted Hookshot Jump off of torches, because they are so short, however if you go next to them and aim up so Link clips inside, you can do an Inverted Hookshot Jump.
You can free the camera during any form of a Hookshot Jump by releasing L target right before you shoot off into the air. This can be useful for navigating through the air as you are falling.