Over the years, I've been testing rugs and carpets over carpeting in large rooms of my house.

Some stay in place, some tug... and some it seems, will never stay in place whatever I do (or can they ? please enlighten me !! )

Is it because the pile of some carpeting is too shag, too dense or not enough, too long (would very short cut pile work?)

If tight, short loop pile works better, like office carpeting for example... when does loop pile start to be too long, or too shaggy and make a top rug tug ?

I've read many articles on the subject, mostly decor and ideas, and seen a multitude of pictures of rug-carpeting arrangements (which I suspect are not always truly livable - they are surely not when copied) and I still don't completely get it...

I know sisal works under rugs, and so do other weaved types carpeting, office loop works too... but what about a fuzzy frieze for example, would that work ?

Can anyone please explain the top rug rule of the under carrying cut pile and/or loop pile ?

Thank you so much for any input !