The line you ask about from Shakespeare's Sonnet 18, the "Shall I compare thee to a summer's day?" sonnet, is:
When in eternal lines to time thou grow'st.
I assume you're wondering about the transversal Shakespeare employs. He takes the verb, grow'st, out of its natural place in the clause and places it at the end. This is a common practice in poetry of Shakespeare's day, and is usually done to create a rhyme. In this poem, "grow'st" is used to rhyme with "ow'st" from line ten.
The grammatically correct word order would create this line:
- When thou grow'st in eternal lines to time.
I assume that's the word order you're looking for.
Transversal is frowned upon by poets today due to its artificiality, but its use was common in Shakespeare's time.