Box - Kids' Poems and Stories With Michael Rosen

The transcript describes a person constructing a box with a lid and locks, large enough to sit inside. The box's walls can move inward by turning a handle from the inside. Once inside, the person experiences the sensation of the box closing in, feeling the pressure and confinement. The narrative concludes with a reflection on the experience, likening it to being a walnut in its shell.

What metaphor does the narrator use to describe their confinement?

What does the phrase 'Walnut in its shell' signify in the context of the text?