Hi @XMech,
A warm welcome to the Bunnings Workshop community and thank you for your question.
It is not the standard use for the 2400 x 900 x 33mm Specrite panels, but I can't see any reason you couldn't use it as a barn door.
The only issue I can foresee, is that barn door roller kits are usually designed for doors that are between 35-45mm thick, but this just means you may need to shorten a couple of bolts. This is relatively easy to do with a hacksaw if needs be.
You might like to check out these Barn door ideas for your home for some examples of similar projects.
Let me know if you have any further questions.
Jacob
