This means escaping 1-tile deep pits with a sandfall overtop without HiJump but with the help of the solid ledge or a frozen enemy.
This also applies to escaping deeper sand pits with HiJump but no sandfall.
This does not include deep sand pits with a sandfall or 1-tile sand pits with no sandfall.
This is done by holding down and then crouch jumping to become unstuck, then transitioning to another action to ascend through the sand.
See also: Tech Page