Mirror Block Erase
From ALttP Speedrunning Wiki
The Mirror Block Erase glitch is used to simply remove movable blocks from the screen completely.
Works on
Exclusive to version JP 1.0 only.
How to perform it
Start pushing a movable block, and use your mirror after it starts moving (but before it ends moving).
You must be indoors, in a non-dungeon room (else the Mirror will only warp you back to the entrance).
