Freeze an enemy at a specific height, stand on it, then fire Grapple horizontally while walking toward a Grapple wall.
The Grapple shot may either contact the Grapple block directly, or it may kill a second enemy.
Either way, if successful, Samus will get clipped slightly inside the wall.
From there, crouch or jump (to force crouch), then fire an angled grapple shot to obtain glitched grapple hanging.
Jumping to force crouch will put Samus in a higher position, which in some positions can allow Samus to grapple to a higher block.
For grappling to the left, Samus' vertical pixel position in hexadecimal must end in 0, 1, 2, 3, 4, 5, 6, 7, or F;
this corresponds to the bottom of Samus' hitbox being between 4 and 12 pixels above the bottom of the tile;
in this case, aim to freeze the enemy so that its top aligns with the mid-point of the tile.
For grappling to the right, Samus' vertical pixel position in hexadecimal must end in 2, 3, 4, 5, 6, or 7;
this corresponds to the bottom of Samus' hitbox being between 7 and 12 pixels above the bottom of the tile;
in this case, aim to freeze the enemy so that its top is slightly above the mid-point of the tile.
See also: Tech Page