Hands up those who have pop riveted and as the rivet breaks the tool jumps and scratches the surrounding area?
For the first 95% of the project I used masking tape (smooth side down) to protect the surroundng area. However when I was riveting the floors I was looking at some anti-slip matting and thought that could be used and it worked a treat for domed rivets.
For flush rivets this method leaves the rivet slightly proud so I would stick to masking tape for those.
Each little piece lasts about 20 rivets. I used a longer strip for rivets next to the side skin to protect both surfaces.
A rare moment of original thought, though I wish I'd thought of this 5 years ago - that's life I suppose!