Julian stands on his toes to lift his body high enough so that he can reach a book. in this example, julian's toes are a:

fulcrum

Explanation:

Fulcrum -

The term is used , to act as a support , is known as fulcrum.

Any support for any task or activity is known as fulcrum .

From the given scenario of the question,

As, Julian takes help or support of her toes in order to gain certain height and take out the book kept at higher level.

Hence,

The toes of Julian act as a fulcrum.