It's interesting what comes up when searching, I was looking for 'felt frame rebate tape', which is used to line the rebate (rabbet) of a frame to cushion and protect the painting, and I found the excellent Knole Conservation Team Blog, which has some frame related posts. It has some fascinating snippets and insights into the handling and treatment of frames at a National Trust house.
The first link is the page I landed on from my search, the text is hard to read in places due to the background images, but still interesting frame related posts:
Second link is the home page:
