Extended Metaphor - tape measure is symbolic of the umbilical cord, suggests they have a strong bond
"Anchor. Kite."
Extended metaphor of the umbilical cord
Mother is restraining her son (the 'Anchor') and the son (the 'Kite') attempts to free himself
"the acres of the walls, the prairies of the floors"
Hyperbolic imagery - embarks theme of exploration, the largeness of the images suggests he's intimidated by the prospect of growing up & gaining independence
"metres, centimetres" , "one-hundredth of an inch"
Semantic field of measurement - could suggest how far speaker could go without his mum
"I reach/ towards a hatch that opens on an endless sky/ to fall or fly."
possible Bird imagery - son is a young bird becoming independent from his mother but doesn't know if he'll succeed without her
"two floors below your fingertips still pinch"
the verb 'pinch' suggests mother wants to cling to her son