Hi BluTopaz,
You can see the specifics of how 10sChick used the floor runner in post #5 here and a search on her posts (you can just click the link) will bring up some of her additional comments as well. Basically she used the floor mat under a topper and then used a sheet on top of the topper.
I’m guessing that you are asking about a mattress protector that is used over a mattress or a mattress/topper combination (vs a mattress cover which is part of the mattress itself). If this is the case then post #89 here and the posts it links to has more information about the pros and cons of different types of mattress protectors and some good sources for each of them that should be helpful.
Phoenix