Hi @boscage,
Thank you for your question about disassembling a shower screen so you can carry out some repairs to tiles beneath.
What you've taken a photo of is a rivet, similar to these Otter Aluminium Blind Rivets.
The only way to remove them is to drill them out. This means they are not reusable and will have to be replaced to reinstall the shower screen.
Unfortunately, I wouldn't advise attempting to remove the shower screen by yourself as the risk of shattering the glass is far too great.
I would suggest contacting a glazier or handyman in your area to assist.
You could use a service such as HiPages or True Local to find someone in your area.
Jacob
