Can anyone help me to rotate an object around an angled line?

Hello.
I have a hatch door on an angled roof (the hatch door tapers with a forced perspective) and want to show it in a half way open position.
I cannot see a way of using the rotate tool to rotate the door group along the angled line of the opening.
Can anyone direct me to help on this?
Many thanks.

If you can identify the axis of rotation with a guideline or an edge, select the hatch, get the rotate tool, click and drag along the roation axis line to align the tool and then rotate as normal.
rotate

That works a treat. Thank you.