How to open florescent light ballast cover?

[JasonM]

I have the florescent light in bathroom, and I want to replace the ballast. I tried to pull out the cover, but somehow it does not come out. How can I open this cover so that I can replace the ballast?

Here are the 3 photos.

Thank you very much.

 

[JasonM]

Thank you.

I found out after posting that by turning the thumb screw half turn or so to align it to the hole, the screw can come out and the cover can be pulled out.

Just in case someone has this problem, I hope this helps.