Hookpushing is a form of ancilla misslotting. Creating a Somaria block in the wrong slot, then using other items to manipulate other slots, allows you to affect the direction and distance that your next use of the hookshot will move you.
- Items that create sprites that remain on the screen for a while -- usually the Master Sword or better to cast sword beams
- A bow and bombs to perform a variant that works in confined spaces
The sprites that remain on the screen for a while are called ancilla, and by manipulating them, you can change the behavior of the hookshot.
Sword beam hookpushing
This example is a useful and satisfying hookpush to learn, because it gets you from the front of Eastern Palace directly to Armos.
Set up your practice ROM
You won't get to watch memory values in a run of the game, but when learning a hookpush, you absolutely want to use the LTTPHack practice ROM.
Here's the configuration I use (relevant part circled):
Performing the hookpush
You want to make a Somaria block in ancilla slot 9, which is an unusual place for a Somaria block to be, so it will be an unusual block.
There is a chance, largely based on the random timing of sword sparkles, that you get a block in ancilla slot 8 instead. It will act different and it won't let you hookpush. If that happens, start over.
Of course you can't look at your ancilla slots while playing the actual game, so learning the setup with the practice ROM, and learning to intuit whether it's going right, is very useful.
In the fourth step above, you'll be spelling "YAY" with your controller buttons. If you press the second Y too soon after the first Y, or too late after the A, it will fail. I find the timing easiest to set up by kicking up boots dust twice, or "YAAY".
If you succeeded, you will get a glitched Somaria block that you can walk under without interacting with it. A Somaria block is ancilla number $2C, so here in the practice hack we can see that it's in slot 9 (the last slot on the HUD).
The preceding step needs to be "a different wall in the same direction", and the effect is subtle but important. The wall that your sword beam hits will form an invisible line that stops your hookpush, which is why it can't be the same wall. In the screenshot, I'm sword-beaming the pot at point-blank range, so the hookpush-stopping line coincides with the right edge of the pot. The wall to the left of the door would also work.
The value in extension slot 0 (here it's $4C) is the distance that your hookpush will take you.
The boss room is directly to the left of the Eastern Palace entrance, so in this example, hookpushing through the wall takes you to the Armos fight.