The hook can be used for grappling (Scroll to change its length), not just linking things together. You can only dislodge 2 vents yourself, the other one is rather unexpected and needs very special equipment but is mostly useless... though its unique because you collide with it after removing it and it's invincible, making it useful for playing with if you do the sandboxy stuff with nails and balloons and such.
The other vents either don't come off, or only come off in specific events, you have no control over them unfortunately.