Proper use of “through” and “threw” can be tricky. Because they sound the same, it can be hard to remember which form is correct.
Remember This Rule
“Through” actually has many meanings, ranging from “in one side and out the opposite” to “among or between.” It can also mean “by way of” or “done or finished.”
Examples:
“He climbed in through the window.”
“She contacted us through her attorney.”
“He pushed his plate away when he was through.”
“Threw” is the past tense of “throw.”
Example:
“He threw the ball.”
Be careful about using “thru.” It is an informal form of "through", and shouldn’t be used in professional writing.