Aiming the hookshot/longshot at a low angle while directly up against a solid surface allows you to shoot through the surface. This can be used to clip out of bounds, or reach other places.
Like the Zelda 64 engine, the collision maps for adjacent rooms are loaded so you're able to hook onto unloaded hookable surfaces.
When you start to strafe against a surface while having hookshot/longshot up, you'll notice that link is clipping into the surface for just a moment. If you release L-Targeting during this, link will stay clipped. Strafing the the right clips further than strafing to the left.
There is different setups for achieving this, two easy ones being
Whenever two walls come together at an outward right angle, there is a certain spot that lacks collision. This spot can be identified in First Person as Link is able to see through the walls. If you strafe into that very spot Link will have the Hookshot out of bounds, which allows for wider angles to use the Hookshot.